WO2023184142A1

WO2023184142A1 - Electrochemical device and electronic device

Info

Publication number: WO2023184142A1
Application number: PCT/CN2022/083643
Authority: WO
Inventors: 刘道林; 林森; 何平
Original assignee: 宁德新能源科技有限公司
Priority date: 2022-03-29
Filing date: 2022-03-29
Publication date: 2023-10-05

Abstract

Disclosed in the present application are an electrochemical device and an electronic device. The electrochemical device comprises a first housing, a second housing, and an isolation member located between the first housing and the second housing. The electrochemical device comprises a first seal part, the first housing comprises a first seal area located at the first seal part, the second housing comprises a second seal area located at the first seal part, and the isolation member comprises a first area located between the first seal area and the second seal area. By making the bonding strength F N/mm between the first seal area and the first area, the tensile strength f N/mm of the isolation member and the stretch rate S of the isolation member satisfy F/(f × S) ≤ 15, and the first seal part has excellent structural reliability.

Description

An electrochemical device and an 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 technique

Currently, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. Since in some application scenarios, a single battery cell cannot achieve the desired output power; therefore, multiple battery cells are usually connected in series, parallel, or mixed, so that the multiple battery cells work together to achieve Desired power output. However, although connecting multiple battery cells in series, parallel or mixed connection can increase the output power, the energy density of the entire battery pack is low. Therefore, the design of series/parallel batteries in the same bag is proposed. The series/parallel battery in the same bag includes a casing and multiple electrode assemblies arranged in the same casing. The series-connected electrode assemblies need to be separated by separators to avoid high voltage. The electrolyte decomposes under voltage, and parallel electrode assemblies are separated by separators to avoid mutual interference.

Contents of the invention

The inventor of this application found through research that when the sealing part of the series/parallel battery pack is bent due to impact, or when the sealing part is folded, it will inevitably cause pulling on the internal separator, thus causing the sealing part to The probability of failure is higher.

In view of the above technical problems, the present application provides an electrochemical device and an electronic device to improve the structural reliability of the sealing part of series/parallel batteries in the same bag.

In order to solve the above technical problems, the first aspect of this application provides an electrochemical device. The electrochemical device includes a first housing, a second housing, and a separator between the first housing and the second housing. The electrochemical device includes a first sealing part, the first housing includes a first sealing area located in the first sealing part, the second housing includes a second sealing area located in the first sealing part, the isolation member includes a first sealing area located in the first sealing area and The first area between the second seal areas. The bonding strength between the first sealing area and the first area is F N/mm, the tensile strength of the spacer is f N/mm, and the stretch rate of the spacer is S, satisfying F/(f×S) ≤15.

By F, f and S satisfying the above relationship, when the first sealing part is bent or folded under impact, on the one hand, the separator itself has sufficient tensile strength and ductility to bend the bending part. The stress and strain are buffered. At the same time, the bonding strength between the isolator and the shell can withstand the stress at the bend, thereby avoiding the occurrence of rupture, making the first sealing part have excellent structural reliability.

In some embodiments, 1≤F/(f×S)≤10. By satisfying F/(f×S)≤10, the tensile strength and ductility of the isolator itself can better buffer the stress and strain at the bend. At the same time, by satisfying F/(f×S)≥1 , the bonding strength between the isolator and the shell can better withstand the stress at the bend, thereby further improving the structural reliability of the first sealing part.

In some embodiments, F≥1. At this time, the isolator and the casing have good bonding strength, which can further suppress the risk of separation between the isolator and the casing, and improve the structural reliability of the first sealing part.

In some embodiments, f≥1. At this time, the isolator itself has good structural strength and can inhibit its own rupture when it is bent and pulled by the first sealing part, thereby improving the structural reliability of the first sealing part.

In some embodiments, S≥9%. At this time, the isolator itself has better ductility and can better buffer the strain when the first sealing part is bent, thereby reducing the risk of rupture of the isolator itself and the connection between the isolator and the housing, and improving the strength of the first sealing part. Structural reliability.

In some embodiments, the number of spacers is n, n≥1, and the electrochemical device satisfies f≥(1+0.1n). In some embodiments, the electrochemical device satisfies S≥(8+n)%. The greater the number of spacers, the greater the bending and pulling stress and strain experienced by the spacers when the first sealing part is bent. By satisfying the above relationship through f and/or S, the spacer itself can further improve its tolerance to bending and pulling. , thereby improving the structural reliability of the first sealing part.

In some embodiments, the thickness of the spacer is H㎜, satisfying H≤0.3.

In some embodiments, the first sealing portion includes a first bending portion. By providing the first bending portion, when the first sealing portion is impacted by an external impact, it can play a buffering role and reduce the pulling force on the internal isolator, thus improving the structural reliability of the first sealing portion.

In some embodiments, the length of the first sealing part is L, and along the length direction of the first sealing part, the coefficient of variation CV of the thickness at both ends and the middle L/2 of the first sealing part is ≤ 5%. By making the thickness variation coefficient CV at both ends and the middle of the first sealing part ≤ 5%, when it is bent along the length direction, the stress everywhere is more balanced, reducing the risk of local rupture due to excessive local stress. , thereby further improving the structural reliability of the first sealing part.

In some embodiments, the first housing further includes a first body part, the first bending part includes a first flanging part and a second flanging part, and the first flanging part is connected to the first body through the second flanging part. parts are connected, and the first flanging part is located between the first main body part and the second flanging part. By arranging the first flanging portion between the first main body portion and the second flanging portion, when the first sealing portion is impacted by an external impact, the first flanging portion can provide a buffering and supporting effect, thereby inhibiting the contact between the second flanging portion and the first sealing portion. Excessive bending at the connection point of the first main body part reduces the pull on the internal isolation member and improves the structural reliability of the first sealing part.

In some embodiments, the electrochemical device further includes a first electrode assembly and a second electrode assembly, the electrochemical device is provided with a first cavity between the first housing and the separator, and the electrochemical device is provided between the second housing and the separator. A second cavity is provided between the isolation members. The first electrode assembly is located in the first cavity, and the second electrode assembly is located in the second cavity. The first electrode assembly and the second electrode assembly are connected in series.

In some embodiments, the isolator 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. The material of the first encapsulation layer and the second encapsulation layer includes the third encapsulation layer. A polymer material. The material of the middle layer includes at least one of a metal material, a second polymer material, or a carbon material.

In some embodiments, the first polymer material includes polypropylene, acid anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyamide, polyester, non- Crystalline α-olefin copolymer or at least one of the derivatives of the above substances.

In some embodiments, the metallic materials include 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 at least one of its compositions or alloys.

In some embodiments, the second polymer material includes 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, acid anhydride modified polypropylene, poly At least one of ethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives of the above substances.

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

A second aspect of the present application also provides an electronic device, including any of the above electrochemical devices.

The electrochemical device provided by this application satisfies F/( f×S)≤15, when the first sealing part is bent or folded under impact, on the one hand, the separator itself has sufficient tensile strength and ductility to reduce the stress and stress at the bending part. The strain is buffered, and at the same time, the bonding strength between the isolator and the shell can withstand the stress at the bend, thereby avoiding the occurrence of rupture, making the first sealing part have excellent structural reliability.

Description of drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. Those of ordinary skill in the art can also obtain other drawings based on the drawings.

Figure 1 is a schematic side view from a first perspective of a battery provided by an embodiment of the present application; wherein, the first sealing portion is to be bent;

Figure 2 is a schematic side view of a battery from a second perspective according to an embodiment of the present application; wherein the first sealing portion is to be bent;

Figure 3 is an exploded schematic diagram of a battery provided by an embodiment of the present application from a first perspective; wherein, the battery has an isolator;

Figure 4 is an exploded schematic diagram of a battery provided by another embodiment of the present application from a first perspective; wherein, the battery has two isolators;

Figure 5 is a schematic side view of the isolator provided by an embodiment of the present application from a first perspective;

FIG. 6 is a schematic side view of the isolator provided by an embodiment of the present application from a second perspective.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is referred to as being "secured" 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 there may be one or more intervening elements present therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the technical field belonging to this application. The terms used in the description of this application are only for the purpose of describing specific embodiments and are not used to limit this application. As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The inventor of this application found through research that the separators in the same-bag series/parallel batteries need to be packaged together with the surroundings of the upper and lower casings, because the introduction of separators into the packaging area poses challenges to the packaging strength and sealing performance. At the same time, when the battery packaging area is bent due to impact, or when the packaging area is folded, there will be a certain pull on the separator. On the one hand, the separator itself needs to ensure that it is not torn. At the same time, it is necessary to prevent the separator from being broken. There are cracks or other failures in the seal of the casing. Especially when there are multiple separators in the battery, the thickness of the packaging area increases, which increases the risk of cracking and failure after the packaging area is bent.

In view of this, referring to FIGS. 1-6 , this embodiment provides an electrochemical device. For convenience of description, in the following embodiment, the electrochemical device is a battery 10 as an example. The battery 10 includes a first case 200 , a second case 300 , and a separator 100 located between the first case 200 and the second case 300 . Battery 10 may also include two or more electrode assemblies. Referring to Figure 3, when the number of the isolator 100 is one, the spacer 100 separates the space enclosed by the first housing 200 and the second housing 300 into two independent spaces, and the number of electrode assemblies can be two. , and the two electrode assemblies are arranged in one-to-one correspondence in the above-mentioned two mutually independent spaces. Referring to FIG. 4 , when the number of isolators 100 is two, the spacers 100 divide the space enclosed by the first housing 200 and the second housing 300 into three mutually independent spaces, and the number of electrode assemblies can be Three, and the three electrode assemblies are arranged in one-to-one correspondence in the above three independent spaces. And so on. For convenience of description, the following description takes as an example that the number of separators 100 is one and the number of electrode assemblies is two. When the number of isolators 100 is one, one side of the isolator 100 is connected to the first housing 200 and the other side is connected to the second housing 300 .

The battery 10 is connected to each other through the first casing 200 , the separator 100 and the periphery of the second casing 300 , for example, by hot melting or gluing, to achieve sealing of the battery 10 and prevent the electrolyte in the battery 10 from being exposed. The shape of the sealing area depends on the shape of the battery 10. In one embodiment, when the battery 10 is a square battery 10, as shown in FIG. 5, the shape of the sealing area may be a rectangular ring and include four sealing edges.

For the convenience of description, no matter what the shape of the sealing area of the battery 10 is, one of the sealing edges of the battery 10 will be used as an example for description below. For ease of distinction, the sealing edge is named the first sealing portion 600 . The tabs 410 of the electrode assembly need to protrude from the sealing edge of the battery 10. The tabs 410 can protrude from the first sealing portion 600 or other sealing edges.

The first housing 200 includes a first sealing area 610 located in the first sealing portion 600 , the second housing 300 includes a second sealing area 630 located in the first sealing portion 600 , and the isolation member 100 includes a first sealing area 610 and a second sealing area 630 located in the first sealing portion 600 . The first area 620 between the two sealing areas 630 is shown in FIG. 5 , where the first area 620 is located in the area 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 area 620 of the spacer 100 is connected to the first sealing area 610 and the other side is connected to the second sealing area 630 . When the number of isolators 100 is multiple, the isolator 100 in this embodiment is the isolator 100 in contact with the first sealing area 610. At this time, the isolator 100 is in contact with the second sealing area through other isolators 800. 630 indirect connection.

In this embodiment, the bonding strength F N/mm between the first sealing area 610 and the first area 620, the tensile strength f N/mm of the spacer 100, and the stretch rate S of the spacer 100 satisfy F/( f×S)≤15. F/(f×S) can specifically be 15, 13, 11, 9, 7, 5 or 3, etc. The specific definitions and test methods of the bonding strength F N/mm, the tensile strength f N/mm of the isolator 100, and the tensile ratio S of the isolator 100 are detailed below. The inventor of this application considered that in order to ensure that the first sealing part 600 is not prone to failure after bending, it is necessary to comprehensively consider the bonding strength FN/mm between the isolator 100 and the housing, and the tensile strength fN/mm of the isolator 100. mm and the stretch rate S of the separator 100, F, f and S satisfy the above relationship. When the first sealing part 600 is bent or folded under impact, on the one hand, the separator 100 It has sufficient tensile strength and ductility to buffer the stress and strain at the bends. At the same time, the bonding strength between the isolator 100 and the shell can withstand the stress at the bends, thereby avoiding rupture. , so that the first sealing part 600 has excellent structural reliability.

In some embodiments, battery 10 may satisfy 1≤F/(f×S)≤10. By satisfying F/(f×S)≤10, the tensile strength and ductility of the isolator 100 can better buffer the stress and strain at the bend. At the same time, by satisfying F/(f×S)≥ 1. The bonding strength between the isolator 100 and the housing can better withstand the stress at the bend, thereby further improving the structural reliability of the first sealing part 600 .

In some embodiments, F ≥ 1 N/mm. At this time, the isolator 100 and the casing have good bonding strength, which can further suppress the risk of separation of the isolator 100 and the casing, and improve the structural reliability of the first sealing part 600 .

In some embodiments, f≥1N/mm. At this time, the isolator 100 itself has good structural strength and can restrain itself from breaking when it is bent and pulled by the first sealing part 600 , thereby improving the structural reliability of the first sealing part 600 .

In some embodiments, S≥9%. At this time, the isolator 100 itself has good ductility and can better buffer the strain when the first sealing part 600 is bent, thereby reducing the risk of rupture of the isolator 100 itself and the connection between the isolator 100 and the housing, and improving the efficiency of the second sealing part 600. A structural reliability of the sealing part 600.

The inventor of the present application also found that the number of spacers 100 has an impact on the structural reliability of the first sealing part 600. In view of this, in one embodiment, the number of spacers 100 is n, n≥1, and satisfies f≥ (1+0.1n)N/mm, for example, when N=1, f≥1.1; when N=3, f≥1.3. In one embodiment, S≥(8+n)% is satisfied. For example, when N=1, S≥9%; when N=3, S≥11%. The inventor of the present application found that the greater the number of spacers, the tensile stress and strain on the spacer 100 will increase accordingly when the first sealing part 600 is bent. By satisfying the above relationship by f and/or S, the isolation can be further improved. The part 100 can withstand pulling, thus improving the structural reliability of the first sealing part 600 .

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

In some embodiments, the first sealing part 600 includes a first bending part 640, that is, the first sealing part 600 is bent at least once. By providing the first bending portion 640 , when the first sealing portion 600 is impacted by an external impact, it can play a buffering role and reduce the pull on the internal isolator, thereby improving the structural reliability of the first sealing portion 600 .

In some embodiments, the length of the first sealing portion 600 is L, and along the length direction of the first sealing portion 600 , the coefficient of variation CV of the thickness at both ends and the middle L/2 of the first sealing portion 600 is ≤ 5%. During the measurement process, three data were measured: the thickness at both ends of the first sealing part 600 and the thickness at the middle position of the first sealing part 600, and then the standard deviation and average value of the three were calculated. The difference between the standard deviation and the average value was calculated. The ratio is the coefficient of variation CV. In this embodiment, the coefficient of variation CV is controlled to ≤ 5%. When the first sealing part 600 is bent along the length direction, the stress everywhere is more balanced, reducing the risk of local rupture due to excessive local stress. risk, thereby further improving the structural reliability of the first sealing part 600

In some embodiments, the first housing 200 further includes a first main body portion 11 , which is a portion of the first housing 200 that is recessed to form a cavity for accommodating the electrode assembly. The first bending portion 640 includes The first flanging portion 641 and the second flanging portion 642 are connected to the first main body portion 11 through the second flanging portion 642, and the first flanging portion 641 is located between the first main body portion 11 and the first flanging portion 642. between the two folded edge portions 642. During the processing of the battery 10, after the first sealing part 600 seals, the first flanging part 641 is bent toward the first main body part 11 relative to the second flanging part 642. Specifically, the first flanging part 641 can be bent to The second flanging portion 642 is stacked and arranged, and the interface between the first flanging portion 641 and the second flanging portion 642 is the folding surface. In some embodiments, the first bending part 640 can also be bent twice, that is, after the first bending part 641 is bent relative to the second bending part 642, the second bending part 642 is also bent toward the second bending part 642. A main body part 11 is bent, specifically, it can be bent until the first flanging part 641 is in contact with the wall surface of the first main body part 11 facing the first bending part 640 . At this time, when the first sealing part 600 receives an external impact, the first flanging part 641 can provide a buffering and supporting effect, inhibit excessive bending at the connection between the second flanging part 642 and the first main body part 11 , and reduce internal isolation. The pulling of the parts improves the structural reliability of the first sealing part 600.

In some embodiments, referring to FIG. 3 , the electrochemical device further includes a first electrode assembly 400 and a second electrode assembly 500 . A first cavity and a second cavity are provided on both sides of the separator 100 . The first electrode assembly 400 is provided with In the first cavity, the second electrode assembly 500 is provided in the second cavity, and the first electrode assembly 400 and the second electrode assembly 500 are connected in series.

In some embodiments, referring to FIG. 6 , the isolator 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 . The first The material of the encapsulation layer 120 and the second encapsulation layer 130 includes the first polymer material. The material of the middle layer 110 includes at least one of a metal material, a second polymer material, or a carbon material.

The separator 100 can be electronically insulating or electronically conductive. Two sides of the separator 100 form independent sealed chambers. Each sealed chamber contains an electrode assembly and an electrolyte to form an electrochemical unit. Wherein, both sides of the separator 100 are in direct contact with the separator of the adjacent electrode assembly and form electrical insulation. At this time, each of the two electrode assemblies leads to at least two tabs 410, and the two electrode assemblies are connected in series or in parallel through the tabs 410.

Metal materials include 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 at least one of its compositions or alloys.

The second polymer material includes 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, acid anhydride modified polypropylene, polyethylene, ethylene propylene copolymer , polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or at least one of the derivatives of the above substances.

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

A second aspect of the present application also provides an electronic device, which includes the electrochemical device in any of the above embodiments.

The electrode assembly of the present application is not particularly limited. Any electrode assembly in the prior art can be used as long as the purpose of the present application can be achieved. For example, a laminated electrode assembly or a wound electrode assembly can be used. The electrode assembly generally includes a positive electrode piece, a negative electrode piece and a separator.

The negative electrode piece in this application is not particularly limited, as long as it can achieve the purpose of this application. For example, a negative electrode plate typically includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, composite current collector, etc. The negative active material layer includes a negative active material. The negative active material is not particularly limited, and any negative active material known in the art can be used. For example, it may include at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like.

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

The electrolyte in this application is not particularly limited, and any electrolyte known in the art can be used, for example, it can be any one of gel state, solid state and liquid state. For example, the liquid electrolyte solution can include lithium salt and non-aqueous solvent.

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

The non-aqueous solvent is not particularly limited as long as it can achieve the purpose of the present application. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, or other organic solvents.

For example, the carbonate compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylene propylene carbonate Ester (EPC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), carbonic acid 1 ,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1 carbonate -Fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluorocarbonate- At least one of 2-methylethylene ester or trifluoromethylethylene carbonate.

The separator in the present application is not particularly limited. For example, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application. 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 base material layer can be a non-woven fabric, film or composite film with a porous structure. The material of the base material layer can be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. kind. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the base material layer. 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 substance.

For example, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited. For example, they can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, and nickel oxide. , at least one of zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is not particularly limited, and may be selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, and polyvinylidene. One or a combination of rrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the polymer material includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).

Hereinafter, embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on weight.

Example 1

Preparation of negative electrode plates

Mix the negative active material graphite, conductive carbon black, and styrene-butadiene rubber in a mass ratio of 96:1.5:2.5, add deionized water, and prepare a slurry with a solid content of 70%, and stir evenly. The slurry is evenly coated on one surface of a copper foil with a thickness of 10 μm, and dried at 110°C to obtain a negative electrode sheet coated with a negative active material layer on one side with a coating thickness of 150 μm, and then the copper foil is Repeat the above coating steps on the other surface of the foil. After the coating is completed, cut the pole piece into a specification of 41mm×61mm and weld the tab 410 for use.

Preparation of positive electrode plates

Mix the cathode active material LiCoO ₂ , conductive carbon black, and PVDF (polyvinylidene fluoride) at a mass ratio of 97.5:1.0:1.5, add NMP, and prepare a slurry with a solid content of 75%, and stir evenly. The slurry is evenly coated on one surface of an aluminum foil with a thickness of 12 μm, and dried at 90°C to obtain a positive electrode sheet coated with a positive active material layer on one side with a coating thickness of 100 μm. Then repeat the above steps on the other surface of the foil. After the coating is completed, the pole piece is cut into a size of 38mm×58mm and the pole tab 410 is welded for use.

Preparation of electrolyte

In a dry argon atmosphere, first mix the organic solvents EC (ethylene carbonate), EMC (ethyl methyl carbonate) and DEC (diethyl carbonate) in a mass ratio of EC:EMC:DEC=30:50:20, and then Add LiPF ₆ (lithium hexafluorophosphate) to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF ₆ concentration of 1.15M.

Preparation of electrode assembly

Use a PE (polyethylene) film with a thickness of 15 μm as the isolation film, place a positive electrode piece on both sides of the negative electrode piece, and place a layer of isolation film between the positive electrode piece and the negative electrode piece to form a stack, and then the entire stack The four corners of the sheet structure are fixed, and the positive electrode tab 410 and the negative electrode tab 410 are drawn out to obtain the electrode assembly.

Preparation of spacer 100

(1) Evenly disperse the encapsulation material PP in the encapsulation layer into the dispersant NMP (N-methylpyrrolidone) to obtain an encapsulation layer suspension, with the concentration of the suspension being 45wt%;

(2) Use a glue coating machine to prepare an encapsulation layer PP with a thickness of 40 μm on both surfaces of the middle layer PET (polyethylene terephthalate) film with a thickness of 20 μm.

(3) The dispersant NMP in the encapsulation layer suspension is dried at 130°C to complete the preparation of the isolation member 100 .

Assembly of the electrode assembly

Place the punched aluminum plastic film (i.e., the first shell 200 in the previous embodiment) with a thickness of 90 μm in the assembly fixture, with the pit surface facing upward, and then place an electrode assembly A in the pit, and then place the isolation The member 100 is placed on the electrode assembly A, one side of the separator 100 is in contact with the diaphragm of the electrode assembly A, and external force is applied to compress it. Place the above-mentioned assembled semi-finished product in another assembly fixture, place the other electrode assembly B on the separator 100, the other side of the separator 100 is in contact with the diaphragm of the electrode assembly B, and then punch out another thickness of A 90 μm aluminum-plastic film (i.e., the second housing 300 in the previous embodiment) is covered with the pit surface downward on the electrode assembly B, and then the two aluminum-plastic films and the separator 100 are heat-sealed together by hot pressing. The electrode assembly A and the electrode assembly B are separated by the separator 100 to obtain an assembled electrode assembly.

Liquid injection packaging

The electrolyte is injected into the two cavities of the above-mentioned assembled electrode assembly and then packaged. The tabs 410 of the two electrode assemblies are led out of the outer packaging. The positive tab 410 of electrode assembly A and the negative tab 410 of electrode assembly B are welded together. Together, series conduction between the two electrode components is achieved.

Example 2

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from PET (polyethylene terephthalate) with a thickness of 30 μm, and the thickness of the encapsulation layer PP is 20 μm. The rest is the same as in Embodiment 1.

Example 3

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from PET (polyethylene terephthalate) with a thickness of 40 μm, and the rest is the same as Embodiment 1.

Example 4

The difference from Embodiment 1 is that in the preparation of the spacer 100, the intermediate layer is selected from an Al layer with a thickness of 25 μm, and the rest is the same as Embodiment 1.

Example 5

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 20 μm, and the thickness of the encapsulation layer PP is 24 μm. The rest is the same as in Embodiment 1.

Example 6

The difference from Embodiment 1 is that in the preparation of the spacer 100, the intermediate layer is selected from an Al layer with a thickness of 22 μm, and the rest is the same as Embodiment 1.

Example 7

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 24 μm, the thickness of the encapsulation layer PP is 32 μm, and the others are the same as in Embodiment 1.

Example 8

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 23 μm, the thickness of the encapsulation layer PP is 35 μm, and the others are the same as in Embodiment 1.

Example 9

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 26 μm, the thickness of the encapsulation layer PP is 38 μm, and the rest is the same as Embodiment 1.

Example 10

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 27 μm, the thickness of the encapsulation layer PP is 34 μm, and the rest is the same as Embodiment 1.

Example 11

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 28 μm, and the thickness of the encapsulation layer PP is 32 μm. The rest is the same as in Embodiment 1.

Example 12

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 25 μm, the thickness of the encapsulation layer PP is 25 μm, and the rest is the same as Embodiment 1.

Example 13

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 24 μm, the thickness of the encapsulation layer PP is 32 μm, and the rest is the same as Embodiment 1.

Example 14

The difference from Embodiment 1 is that in the preparation of the spacer 100, the intermediate layer is selected from an Al layer with a thickness of 20 μm, and the rest is the same as Embodiment 1.

Example 15

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 25 μm, the thickness of the encapsulation layer PP is 20 μm, and the rest is the same as in Embodiment 1.

Example 16

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 14 μm, the thickness of the encapsulation layer PP is 22 μm, and the others are the same as in Embodiment 1.

Example 17

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 20 μm, the thickness of the encapsulation layer PP is 30 μm, and the rest is the same as Embodiment 1.

Comparative example 1

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 12 μm, the thickness of the encapsulation layer PP is 20 μm, and the others are the same as in Embodiment 1.

Comparative example 2

The difference from Embodiment 1 is that in the preparation of the isolator 100, the intermediate layer is selected from an Al layer with a thickness of 10 μm, the thickness of the encapsulation layer PP is 15 μm, and the others are the same as in Embodiment 1.

Test of bonding strength F

Take a sample of the sealing area with a width W ₁ (for example, W ₁ can be 8mm), use a multi-functional tensile tester, clamp the materials on both sides of the sealing area, and take the tensile speed to 50mm/min, conduct the test, and obtain the peeling result If the tensile force is P ₁ , then the bonding strength F = P ₁ /W ₁ . For example, when measuring the bonding strength F between the first sealing area 610 and the first area 620, the first sealing portion 600 with a width W ₁ can be cut out, and a multifunctional tensile tester can be used to clamp the first sealing portion 600 respectively. The shell 200 and the isolator 100 are stretched at a speed of 50 mm/min to obtain the pulling force P ₁ for peeling off the two. Then the bonding strength between the first sealing area 610 and the first area 620 is F = P ₁ /W ₁ .

Testing of tensile strength f and stretch rate S

Take 100 samples of spacers with width W ₂ (for example, W ₂ can be 15mm), use a multifunctional tensile tester, clamp both ends of the sample, the initial length of the spacer between the clamps is K, and the tensile speed is 50mm/min, conduct the test. When the isolator 100 is broken, the breaking tensile force value P ₂ and the maximum tensile length L are obtained, then the tensile strength f=P ₂ /W ₂ ; the tensile rate S=(LK)/K.

Seal structure stability test

Conduct a bending test on the sealing parts on both sides. That is, the sealing part takes the boundary between the sealing part and the main body of the casing as the axis, and first bends toward the upper half of the side wall of the main body of the casing until the sealing part and the side wall The upper part of the piece fits together and is counted as one bend. Then bend it 180° in the opposite direction to fit the lower part of the side wall, which is recorded as a second bend. Repeat this process, the sealing part on one side is bent 100 times, and the sealing part on the other side is bent 200 times. Disassemble the battery and observe whether cracks appear at the connection between the isolators and the casing of the seals on both sides. The following three states are defined: ① If the length of the crack accounts for more than 10% of the length of the seal, it is defined as a serious crack; ② If the length of the crack If the ratio to the length of the seal is greater than 0% and less than 10%, it is defined as a slight crack; and ③ no cracks.

Table 1 shows the parameters of the spacers and the structural stability of the sealing part in each embodiment and comparative example.

Table 1

As shown in Table 1, in Comparative Examples 1 and 2, since F/(f×S) is greater than 15, the structural stability of the sealing part is poor, and serious cracks appear in both cases. In Examples 1-17, which satisfy F/(f×S)≤15, no serious cracks occurred in the sealing part of the corresponding battery, and the structural stability of the sealing part was good. This is because, on the one hand, the isolator itself has sufficient tensile strength and ductility to buffer the stress and strain at the bends, and at the same time, the bonding strength between the isolator and the shell can withstand the stress at the bends. Stress, thereby avoiding the occurrence of cracks, making the first sealing part have excellent structural reliability. In addition, for the case where there are multiple spacers, as shown in Examples 14-17, if f≥(1+0.1n), and/or S≥(8+n)% is satisfied, the structural reliability of the sealing part can be ensured .

Furthermore, from the comparison between Examples 1-10 and Examples 11-13, it can be seen that the coefficient of variation of the sealing portion thickness CV≤5% is further satisfied, and the structural reliability of the corresponding battery sealing portion is further improved. This is because by making the thickness variation coefficient CV at both ends and the middle of the seal part ≤ 5%, when it is bent along the length direction, the stress everywhere is more balanced, reducing local cracking caused by excessive local stress. risk, thereby further improving the structural reliability of the sealing part.

It should be noted that the preferred embodiments of the present application are given in the description and drawings of this application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not used as additional limitations on the content of the present application, and are provided for the purpose of making the disclosure of the present application more thorough and comprehensive. Moreover, the above technical features can be continuously combined with each other to form various embodiments not listed above, which are all deemed to be within the scope of the description of this application; further, for those of ordinary skill in the art, they can be improved or transformed according to the above description. , and all these improvements and transformations should fall within the protection scope of the claims appended to this application.

Claims

An electrochemical device, characterized in that it includes a first housing, a second housing, and an isolation member located between the first housing and the second housing;

The electrochemical device includes a first sealing part, the first housing includes a first sealing area located in the first sealing part, and the second housing includes a second sealing area located in the first sealing part. , the isolation member includes a first area located between the first sealing area and the second sealing area;

The bonding strength between the first sealing area and the first area is F N/mm, the tensile strength of the isolator is f N/mm, and the stretch rate of the isolator is S, Satisfies F/(f×S)≤15.
The electrochemical device according to claim 1, characterized in that at least one of the following conditions (1)-(4) is met:

(1)1≤F/(f×S)≤10;

(2)F≥1;

(3)f≥1;

(4)S≥9%.
The electrochemical device according to claim 1, characterized in that the number of the spacers is n, n≥1, and the electrochemical device satisfies at least one of the following conditions (5)-(6):

(5)f≥(1+0.1n);

(6)S≥(8+n)%.
The electrochemical device according to claim 1, characterized in that at least one of the following conditions (7)-(8) is met:

(7) The thickness of the isolator is H㎜, satisfying H≤0.3;

(8) The first sealing part includes a first bending part.
The electrochemical device according to claim 1, characterized in that

The length of the first sealing part is L. Along the length direction of the first sealing part, the coefficient of variation CV of the thickness at both ends and the middle L/2 of the first sealing part is ≤ 5%.
The electrochemical device according to claim 4, characterized in that

The first housing further includes a first main body portion, the first bending portion includes a first flanging portion and a second flanging portion, and the first flanging portion is connected to the second flanging portion through the second flanging portion. The first main body part is connected, and the first flanging part is located between the first main body part and the second flanging part.
The electrochemical device according to claim 1, characterized in that

The electrochemical device further includes a first electrode assembly and a second electrode assembly. The electrochemical device is provided with a first cavity between the first housing and the isolator. A second cavity is provided between the second housing and the isolator, the first electrode assembly is located in the first cavity, and the second electrode assembly is located in the second cavity. The first electrode assembly and the second electrode assembly are connected in series.
The electrochemical device according to claim 1, characterized in that

The isolator 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. The first encapsulation layer and the second encapsulation layer The material of the encapsulation layer includes a first polymer material; the material of the intermediate layer includes at least one of a metal material, a second polymer material, or a carbon material.
The electrochemical device according to claim 8, characterized in that

The first polymer material includes polypropylene, acid anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyamide, polyester, amorphous α- At least one of olefin copolymers or derivatives of the above substances;

The metal materials include 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 at least one of its compositions or alloys;

The second polymer material includes 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, polycarbonate Propyl ester, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene propylene At least one of copolymers, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives of the above substances;

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