CN112002868B

CN112002868B - Electrochemical device and electronic device

Info

Publication number: CN112002868B
Application number: CN202010937408.7A
Authority: CN
Inventors: 张楠; 张益博; 严坤; 胡乔舒
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2021-07-20
Anticipated expiration: 2040-09-08
Also published as: CN114156607A; CN112002868A

Abstract

The application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises at least two electrode assemblies and a packaging shell, wherein the electrode assemblies are respectively arranged in independent cavities in the packaging shell; each electrode assembly comprises two lugs with opposite polarities, wherein at least one lug of one electrode assembly is connected with one of the two lugs of the other electrode assembly, and orthographic projections of the two connected lugs in the thickness direction Z of the seal have lug overlapping areas; and observing along the thickness direction Z of the seal, wherein the overlapping width of the two connected tabs accounts for 40% < alpha < 100% of the width of any tab along the length direction X of the seal at the outer edge of the seal of the packaging shell. The electrochemical device provided by the application not only realizes high voltage output, but also improves the packaging reliability of the tab area during high voltage output.

Description

Electrochemical device and electronic device

Technical Field

The present invention relates to the field of electrochemistry, and more particularly, to an electrochemical device and an electronic device using the same.

Background

Lithium ion batteries have many advantages of large volumetric and mass energy density, long cycle life, low self-discharge rate, small volume, light weight, etc., and have wide applications in the consumer electronics field. With the rapid development of electric automobiles and mobile electronic devices in recent years, people have increasingly high requirements on energy density, safety, cycle performance and the like of batteries, and the appearance of novel lithium ion batteries with comprehensively improved comprehensive performance is expected.

Disclosure of Invention

An object of the embodiments of the present application is to provide an electrochemical device and an electronic device, which achieve high voltage output and improve welding reliability of two tabs connected in series and parallel and packaging reliability of a tab region.

A first aspect of the present application provides an electrochemical device comprising at least two electrode assemblies and a package case, the electrode assemblies being respectively disposed in separate cavities within the package case;

each electrode assembly comprises two lugs with opposite polarities, wherein at least one lug of one electrode assembly is connected with one of the two lugs of the other electrode assembly, and orthographic projections of the two connected lugs in the thickness direction Z of the seal have lug overlapping areas;

the proportion of the overlapping width O1 of the two connected tabs in the width W1 of any tab is more than 40 percent and alpha is less than or equal to 100 percent;

wherein the overlapping width O1 is the overlapping width of the two connected tabs along the seal length direction X at the outer edge of the seal of the package shell as viewed along the seal thickness direction Z;

the tab width W1 is observed along the seal thickness direction Z, the outer edge of the seal of the packaging shell is along the seal length direction X, and the width of any tab in the two connected tabs is equal to the width of the tab in the two connected tabs.

In some embodiments of the first aspect of the present application, tab glue is disposed on each of the two connected tabs, and the tab glue width disposed on the tab exceeds the two sides of the tab along the length direction X of the seal at the outer edge of the seal of the package casing, and the ratio of the tab glue shoulder width D2 to the tab width W1 is D2/W1 ≥ 1/60;

the tab glue shoulder width D2 is the distance between one side of the tab glue and the edge of the tab on the same side along the X direction at the outer edge of the package shell seal.

In some embodiments of the first aspect of the present application, an orthographic projection of tab glue on the two connected tabs in the sealing thickness direction Z has a tab glue overlapping area, and a ratio of a tab glue overlapping width O2 to any tab glue width W2 is 40% < β ≦ 100%;

the overlapping width O2 of the tab glue is the overlapping width of the tab glue at the outer edge of the seal of the packaging shell along the length direction X of the seal, observed along the thickness direction Z of the seal;

the width W2 of the tab glue is observed along the thickness direction Z of the seal, and the width of any tab glue in the tab glue is observed along the length direction X of the seal at the outer edge of the seal of the packaging shell.

In some embodiments of the first aspect of the present application, the distance between the two tabs of the connection is D5 at the package envelope outer edge; the two connected tabs are provided with a connecting area, and the length of the tab between the connecting area and the outer edge of the packaging shell seal is D6; the relationship between D5 and D6 satisfies: 0< D5/D6 is less than or equal to 1.7.

In some embodiments of the first aspect of the present application, 3mm ≦ D6 ≦ 30 mm.

In some embodiments of the first aspect of the present application, 0.1mm < D5 ≦ (H1+ H2)/2+5mm, where H1 and H2 are the thicknesses of two adjacent electrode assemblies, respectively, and H1 and H2 may be the same or different.

In some embodiments of the first aspect of the present application, the area of the connection region S1 is 1mm²To 200mm²。

In some embodiments of the first aspect of the present application, the tab glue exceeds the package casing upper edge along the seal width direction Y by a distance of 0.2mm or more and D1 or less and 5mm or less, the tab glue has a thickness of 0.1mm or more and D3 or more and 3mm or less, and the tab thickness of 0.2mm or more and D4 or less and 5mm or less in the direction away from the electrode assembly.

In some embodiments of the first aspect of the present application, α is 50% ≦ 100%.

In some embodiments of the first aspect of the present application, the two tabs that are connected are two tabs of opposite polarity.

In some embodiments of the first aspect of the present application, the electrode assembly has tabs extending from different directions out of the package can.

In some embodiments of the first aspect of the present application, the electrochemical device further comprises a separator between the electrode assemblies, the separator having a thickness of 2 μm to 100 μm.

In some embodiments of the first aspect of the present application, the structure of the electrode assembly includes at least one of a wound structure and a laminated structure.

In some embodiments of the first aspect of the present application, the package housing comprises at least one of an aluminum plastic film, an aluminum housing, a steel housing, a plastic housing.

In a second aspect, an electronic device is provided that includes an electrochemical device provided in the first aspect of the present application.

The application provides an electrochemical device through the inside series connection mode of a plurality of electrode subassemblies, has realized high voltage output, has the effect that reduces the total heat production of electrochemical device, reduces the temperature rise simultaneously. Different electrode assemblies are respectively arranged in independent cavities, so that the electrode assemblies are ensured to be in a liquid electrolyte environment, the problem of internal short circuit and the problem of electrolyte decomposition under high pressure are avoided, and the safety performance of the electrochemical device is improved. Through the effective connection between the lugs of the adjacent electrode assemblies, the connection reliability is improved, the effective electric energy output and the overcurrent capacity of the high-voltage electrochemical device are ensured, the electric energy consumption caused by the heat production of the lugs is reduced, the softening or melting of lug glue caused by the heating of the lugs is also avoided, and the packaging reliability of the electrochemical device is improved. The electrode lugs are led out of the packaging shell, the relative positions of the electrode lugs are designed and regulated, and the electrode lug consistency is designed, so that the packaging reliability of the electrochemical device with high output voltage is further improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application.

FIG. 1 is a schematic structural view of an electrochemical device according to an embodiment of the present disclosure;

FIG. 2 is a schematic structural view of an electrochemical device according to another embodiment of the present disclosure;

FIG. 3 is a schematic structural view of an electrochemical device according to still another embodiment of the present application;

FIG. 4 is a partial schematic structural view of the left side view of FIG. 2;

FIG. 5 is another partial schematic structural view of the left side view of FIG. 2;

fig. 6 is a partial schematic view of the left side view of fig. 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by referring to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments.

The electrochemical device of the present application may be any electrochemical device known to those skilled in the art, such as a lithium ion battery, a sodium ion battery, a magnesium ion battery, a supercapacitor, and the like, and the following description will be given by taking a lithium ion battery as an example. It is to be understood by one skilled in the art that the following description is illustrative only and is not intended to limit the scope of the present application.

The application provides an electrochemical device, which comprises at least two electrode assemblies and a packaging shell, wherein the electrode assemblies are respectively arranged in independent cavities in the packaging shell;

Fig. 1 shows an embodiment of the present application, a three-dimensional coordinate system is established with a seal length direction, a seal width direction and a seal thickness direction, an X direction indicates the seal length direction, a Y direction indicates the seal width direction, and a Z direction indicates the seal thickness direction, the electrochemical device includes an electrode assembly disposed in a separate cavity in a package can 1, for example, a first electrode assembly and a second electrode assembly disposed in separate cavities in the package can 1 and separated by a separator 8, each electrode assembly includes two tabs 2 having opposite polarities, at least one tab 2 of one electrode assembly is connected with one of the two tabs of the other electrode assembly, and orthographic projections of the connected two tabs 2 in the seal thickness direction Z have tab overlapping regions.

Referring to fig. 2, the package 1 has a seal area 5 thereon, and a dotted line parallel to the X direction in the seal area 5 shows the outer edge of the seal of the present application, which is known as the upper boundary of the seal area 5; each electrode assembly has two tabs of opposite polarities, one of the tabs 2 is connected to one of the two tabs of the other electrode assembly, and an orthogonal projection in the seal thickness direction Z has a tab overlapping region 4. Observing along the thickness direction Z of the seal, wherein the overlapping width of the two connected tabs is O1 along the length direction X of the seal at the outer edge of the seal of the packaging shell 1; observing along the thickness direction Z of the seal, wherein the width of any one of the two connected tabs is W1 along the length direction X of the seal at the outer edge of the seal of the packaging shell 1; the proportion of O1 in W1 is more than 40 percent and less than or equal to alpha and less than or equal to 100 percent.

In the electrochemical device of the present application, each electrode assembly may include one positive electrode tab and one negative electrode tab, and the adjacent electrode assemblies may be connected to each other by the positive electrode tab and the negative electrode tab, thereby realizing the series connection between the adjacent electrode assemblies. The tab overlapping region may affect the transmission of electrical energy between adjacent electrode assemblies, and is not limited to any theory, and when the overlapping width is small, the packaging reliability of two connected tabs may be reduced, and further, the packaging reliability of two adjacent electrode assemblies may be affected. In the electrochemical device, the proportion alpha of the width O1 of the tab overlapping area of two connected tabs to any tab width W1 is as follows: alpha is more than 40 percent and less than or equal to 100 percent, preferably more than or equal to 50 percent and less than or equal to 100 percent, not only can the effective electric energy output and the overcurrent capacity of the high-voltage electrochemical device be ensured, but also the packaging reliability between adjacent electrode assemblies can be ensured.

In some embodiments of the present application, tab glue is disposed on each of two connected tabs, and the tab glue disposed on the tab has a width exceeding both sides of the tab along the length direction X of the seal at the outer edge of the seal of the package casing, and the ratio of the tab glue shoulder width D2 to the tab width W1 is D2/W1 ≥ 1/60. As shown in fig. 2, in the present application, the tab glue shoulder width D2 is the distance that one side of the tab glue exceeds the edge of the tab on the same side along the X direction at the outer edge of the package casing seal, and the tab glue shoulder widths on the two sides may be equal or unequal. The ratio D2/W1 within the above range can ensure the packaging reliability of the electrochemical device.

In some embodiments of the present application, the width W1 of the tab is: w1 is more than or equal to 2mm and less than or equal to 60 mm. The width W1 of the tab directly affects the area of the overlapping region of the tab, and the width W1 of the tab is within the above range, so that the connection reliability between adjacent electrode assemblies can be effectively improved.

In some embodiments of the present application, the orthographic projection of the tab glue on the two connected tabs along the sealing thickness direction Z has a tab glue overlapping area, and the proportion β of the tab glue overlapping width O2 to any tab glue width W2 is: beta is more than 40 percent and less than or equal to 100 percent;

Fig. 3 shows an embodiment of the present application, the tab glue 3 on the two tabs being connected has a tab glue overlapping area 6, along the seal length direction X, at the seal outer edge of the package case 1, the width O2 of the tab glue overlapping area 6 accounts for the ratio β of the width W2 of any tab glue at the seal outer edge of the package case 1: beta is more than 40 percent and less than or equal to 100 percent. The tab overlapping region 6 can also affect the packaging reliability of two connected tabs, when the width of the tab overlapping region 6 is small, the tab is bent by external force on the electrochemical device, the junction of the two connected tabs is easy to generate strain of the tabs to the plane perpendicular to the tabs, and the junction generates stress, so that cracks are easily generated, and the packaging reliability of the two connected tabs is reduced. The proportion of the width of the tab glue overlapping region 6 to the width of any tab glue is within the above ratio range, so that the packaging reliability between adjacent electrode assemblies can be further improved.

In some embodiments of the present application, referring to fig. 3 and 5, at the outer edge of the seal of the packaging shell 1, the distance between the two tabs of the connection is D5; the two tabs connected have a connection region 7, the tab length D6 between the connection region 7 and the outer edge of the seal of the packaging shell 1; the relationship between D5 and D6 satisfies: 0< D5/D6 ≦ 1.7, preferably 3X 10^-3＜D5/D6≤1.5。

In some embodiments of the present application, 0.1mm < D5 ≦ (H1+ H2)/2+5 mm. Wherein, the distance D5 between the two connected tabs refers to the distance between the two connected tabs at the outer edge of the package sealing, H1 and H2 are the thicknesses of two adjacent electrode assemblies, respectively, and H1 and H2 may be the same or different. When the distance between two utmost point ears is too big, not only can increase the connection degree of difficulty of two utmost point ears, can reduce the connection reliability between two utmost point ears of connecting moreover. Therefore, the connection reliability between the adjacent electrode assemblies can be improved by designing and controlling the relative positions of the two tabs to be connected. The distance between two tabs connected in this application refers to the distance between the two tabs in the thickness direction Z of the seal at the outer edge of the tab and the seal of the packaging shell.

Fig. 3 shows an embodiment of the application, the two tabs being connected having a connection area 7, D6 referring to the tab length between the lower edge of the connection area 7 and the outer edge of the seal of the packaging shell 1. When the ratio of D5/D6 is small, D6 is large, that is, the connection region 7 is far away from the electrode assembly and the distance from the electrode assembly is large, and when the electrochemical device is subjected to an external force, the tab 2 having a sufficient length relieves stress, reducing stress to the end seal and the connection, so that the seal reliability and the connection reliability between adjacent two electrode assemblies are improved. When the ratio of D5/D6 is large, D5 is large, that is, the distance between two connected tabs is too large, when the electrochemical device is subjected to an external force, the seal area is damaged by tearing the tab 2, thereby affecting the packaging reliability of the electrochemical device and the stability of the connection area 7. In the electrochemical device provided in the present application, the ratio of D5/D6 satisfies the above range, and not only the connection reliability between adjacent two electrode assemblies but also the packaging reliability of the electrochemical device can be improved.

In some embodiments of the present application, 3mm ≦ D6 ≦ 30 mm. When D6 is small, tab glue on the tabs is easily damaged when two tabs are connected, the packaging reliability of the electrochemical device is influenced, and the connection operation difficulty is high; secondly, because the connection area is close to the packaging shell, cracks are easy to generate under the action of external force, so that the connection reliability of two adjacent electrode assemblies is reduced; thirdly, the connection area is close to the package case, and the connection strength of the connection area is affected due to the fact that the electrode assemblies have certain thicknesses, so that the connection reliability of two adjacent electrode assemblies is reduced; moreover, when the connection is not tight enough due to low connection strength of the connection region, the resistance of the connection region is increased in the use process of the electrode assembly, so that the temperature rise of the tab is increased during charging, the tab glue is softened or melted, and the packaging reliability of the electrochemical device is reduced. When D6 is large, the connection region is more easily broken when the electrochemical device is subjected to external force, so that the connection reliability between the adjacent two electrode assemblies is reduced, and when D6 is large, the connection region increases the volume of the electrochemical device, which results in a reduction in the volumetric energy density of the electrochemical device because the connection region is an inactive material region and does not supply energy. Therefore, when D6 is within the above range, the resulting electrochemical device has excellent packaging reliability and use reliability.

In some embodiments of the present application, the area of the connection region S1 is 1mm²To 200mm². The area S1 of the connection region is smaller than or equal to the area of the tab overlapping region, that is, the tab overlapping region may be connected entirely or may be heavyOverlap the region and carry out partial connection, as long as can ensure the connection reliability of two utmost point ears, realize the purpose of this application can. When the area of the connection region is too small, the connection reliability between the two tabs to be connected is reduced, and the current-carrying capacity of the connection region becomes small. The connection reliability between adjacent electrode assemblies and the normal work of the electrochemical device can be effectively guaranteed within the area range of the connection area, the current carrying capacity is improved along with the increase of the area S1 of the connection area, and the effective electric energy output and the overcurrent capacity of the high-voltage electrochemical device are guaranteed. In addition, the increase of the area S1 of the connection area can also reduce the heat generation of the tabs and the consumption of electric energy, thereby avoiding the softening or melting of tab glue caused by the heat generation of the tabs and improving the packaging reliability of the electrochemical device.

Further, when the area S1 of the connection region is not changed, the width of the tab overlapping region is reduced, the width of the connection region in the seal length direction X is reduced, the connection strength of the connection region is reduced, and the connection reliability of the adjacent electrode assemblies is also reduced.

In some embodiments of the present application, along keeping away from the electrode assembly direction, tab glue 3 surpasses along seal width direction Y the distance of packaging shell upper edge is 0.2mm ≦ D1 ≦ 5mm, the shoulder width of tab glue 3 is 1mm ≦ D2 ≦ 8mm, as shown in FIG. 4, the thickness of tab glue 3 is 0.1mm ≦ D3 ≦ 3mm, the thickness of tab 2 is 0.2mm ≦ D4 ≦ 5 mm. When D1 to D4 are within the above range, the resulting electrochemical device has good packaging reliability and use reliability, and adjacent electrode assemblies have good connection reliability.

In the application, the tab glue arranged on the tab can be combined with the packaging shell, and the combination can be that the tab is connected with the packaging shell in a sealing way through the tab glue.

In some embodiments of the present application, the two tabs of each electrode assembly may protrude out of the pack case from the same direction or different directions. The extending directions of the two tabs can be one edge of the packaging shell, and can also be one extending from any two edges of the packaging shell.

As shown in fig. 5, in some embodiments of the present application, the electrochemical device may further include a separator 8 between the electrode assemblies, the cavities are located at both sides of the separator 8, and each electrode assembly may be disposed in a separate cavity. Wherein the thickness of the separator is 2 μm to 100 μm, preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm. In an electrochemical device, the separator should not only have ion-insulating properties, but also have mechanical strength. Therefore, if the separator is too thin, the mechanical strength is poor, and the separator is easily damaged to affect the performance and safety of the electrochemical device. Too thick a separator increases the weight of the electrochemical device, so that the performance of the electrochemical device is limited. In other embodiments of the present application, as shown in fig. 6, in order to achieve effective bonding between the tab paste 3 and the separator 8, a bonding material 9 is further included on the separator 8.

In some embodiments of the present application, the structure of the electrode assembly includes at least one of a winding structure and a lamination structure.

In some embodiments of the present application, the cavity is a sealed cavity. The sealed cavity is formed by hermetically connecting the partition board and the packaging shell, independent cavities are formed on two sides of the partition board, and the electrode assemblies and the electrolyte on two sides of the partition board are completely separated, so that the normal work of the electrode assemblies on two sides can be guaranteed, and the good sealing performance is also favorable for improving the safety and the environmental stability of the electrochemical device.

In the present application, the connection method of the two tabs to be connected is not particularly limited as long as the object of the present application can be achieved. For example a welded connection. The manner of the above-described welded connection is not particularly limited as long as the object of the present application can be achieved. Such as laser welding, ultrasonic welding, or resistance welding, among others.

In the present application, when the two tabs to be connected are connected by welding, the area of the connection region is the area surrounded by the outermost peripheral welding points, and the welding points are distributed in the connection region.

The electrode assembly referred to in the present application may be an electrode assembly including a positive electrode tab, a negative electrode tab, and a separator, and is explained by way of example of the above electrode assembly. It is to be understood by one skilled in the art that the following description is illustrative only and is not intended to limit the scope of the present application.

In the present application, the thickness of the electrode assembly is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the electrode assembly is 3 mm.

In some embodiments of the present application, the positive electrode sheet 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. In the present application, the positive electrode current collector is not particularly limited, and may be any positive electrode current collector known in the art, for example, a copper foil, an aluminum alloy foil, a composite current collector, and the like. The positive electrode active material is not particularly limited and may be any positive electrode active material of the prior art, for example, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium iron manganese phosphate. In the present application, the thickness of the positive electrode current collector and the positive electrode active material is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 8 to 12 μm, and the thickness of the positive electrode active material is 30 to 120 μm.

In some preferred embodiments of the present application, the positive electrode tab may further include a conductive layer between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

In some embodiments of the present application, the negative electrode tab 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. In the present application, 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 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, mesocarbon microbeads, silicon carbon, silicon oxy-compound, soft carbon, hard carbon, lithium titanate, or niobium titanate may be included. In the present application, the thickness of the anode current collector and the anode active material is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 6 to 10 μm, and the thickness of the negative electrode active material is 30 to 120 μm.

In some preferred embodiments of the present application, the negative electrode tab may further include a conductive layer between the negative electrode current collector and the negative electrode active material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

The above-mentioned conductive agent is not particularly limited, and any conductive agent known in the art may be used as long as the object of the present application can be achieved. For example, the conductive agent may include at least one of conductive carbon black (Super P), Carbon Nanotubes (CNTs), carbon fibers, graphene, or the like. The adhesive is not particularly limited, and any adhesive known in the art may be used as long as the object of the present application can be achieved. For example, the binder may include at least one of Styrene Butadiene Rubber (SBR), polyvinyl alcohol (PVA), Polytetrafluoroethylene (PTFE), sodium carboxymethylcellulose (CMC-Na), or the like.

In some embodiments of the present application, the separator is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the separator may be 5 μm to 15 μm, and the separator may include a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, or the like. In the present application, the diaphragm may also be referred to as a separator.

For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. 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 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 a layer formed by mixing a polymer and an inorganic substance.

For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited and may be, for example, at least one selected from the group consisting 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. 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 comprises a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

The tab referred to in this application refers to a metal conductor that is drawn from the positive electrode tab or the negative electrode tab and is used to connect other parts of the electrochemical device in series or in parallel. The positive pole tab is led out from the positive pole piece, and the negative pole tab is led out from the negative pole piece.

The material of the tab jelly is not particularly limited in the present application, and any tab jelly known in the art may be used as long as the object of the present application is achieved. For example, the material of the tab glue may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or the like, and may further include a composite material including the above-mentioned polymer, for example, a PP/PET/PP composite material, a PP/PEN/PP composite material, a PP/non-woven fabric/PP composite material, a PP/high temperature barrier layer/PP composite material, or the like. The width of the tab glue is not particularly limited as long as the object of the present application can be achieved. For example, the width of the tab paste is 4mm to 76 mm. The nonwoven fabric is not particularly limited as long as the object of the present application can be achieved, and examples thereof include polypropylene nonwoven fabrics, polyethylene nonwoven fabrics, and the like. The high-temperature barrier layer is not particularly limited as long as the object of the present application can be achieved, and for example, an aramid layer or the like.

The separator is not particularly limited in the present application, and any separator known in the art may be used as long as the object of the present application can be achieved. Generally, the separator is required to have ion insulation properties so as to prevent high-pressure decomposition of the electrolyte and short circuits in the electrode assembly. For example, the material of the separator includes at least one of a polymer material, a metal material, a carbon material, or a composite material thereof.

The polymer material is not particularly limited as long as the present application can be achieved, and any material known to those skilled in the art may be used, and for example, the polymer material may include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyethylene terephthalate, polyethylene naphthalate copolymer, polyethylene naphthalate, polyethylene terephthalate, and polyethylene terephthalate, and polyethylene terephthalate, and polyethylene naphthalate, and polyethylene terephthalate, and/polypropylene, and polyethylene terephthalate, or the like, At least one of ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous alpha-olefin copolymer, and derivatives thereof.

The metal material is not particularly limited, and any material known to those skilled In the art may be used as long as the object of the present application can be achieved, and may include, for example, 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, and a composition or alloy thereof. Preferably, a metal material having good oxidation and reduction resistance in a lithium ion battery environment may be selected.

The carbon material includes at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerene, a conductive graphite film, or a graphene film. In some embodiments of the present application, the ion insulating layer is preferably made of a polymer material, and since the density of the polymer material is low, the weight of the inactive material can be reduced, thereby increasing the mass energy density of the electrode assembly. In addition, the ion insulating layer is made of high polymer materials, so that the probability of generating fragments is lower under mechanical abuse conditions (such as nail penetration, impact and extrusion), and the wrapping effect on the damaged surface of a machine is better, so that the safety boundary under the mechanical abuse conditions can be improved, and the safety test passing rate is improved.

In some embodiments of the present application, the separator further includes an encapsulation layer, the encapsulation layer may be disposed on both sides of the ion insulation layer, the encapsulation layer is disposed on the peripheral edge of the surface of the ion insulation layer or on the entire surface thereof, and the encapsulation layer is used for sealing and connecting the ion insulation layer and the package case.

In the present application, the material of the encapsulation layer is not particularly limited as long as the object of the present application can be achieved, and materials well known to those skilled in the art may be used, for example, the encapsulation layer material includes at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α -olefin copolymer, and derivatives thereof.

Of course, the encapsulation layer of the present application also has an ion insulating function when covering the entire surface of the ion insulating layer. In the present application, the separator is divided into the ion insulating layer and the encapsulating layer for convenience, and does not mean that the encapsulating layer has no ion insulating property. For example, when the ion insulating layer covers the entire encapsulation layer on both sides, the ion insulating layer and the encapsulation layer function together as ion insulation.

In the present application, the coupling material between the separator and the tab paste is not particularly limited as long as the object of the present application can be achieved, and a material known to those skilled in the art may be used, for example, the coupling material includes at least one of polypropylene, polyester, parahydroxybenzaldehyde, polyamide, polyphenylene ether, polyurethane, and the like.

The electrolyte referred to herein may comprise a lithium salt and a nonaqueous solvent. In the present application, 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 LiPF₆、LiBF₄、LiAsF₆、LiClO₄、LiB(C₆H₅)₄、LiCH₃SO₃、LiCF₃SO₃、LiN(SO₂CF₃)₂、LiC(SO₂CF₃)₃Or LiPO₂F₂At least one of (1). For example, LiPF is used as lithium salt₆. In the present application, the nonaqueous solvent is not particularly limited as long as the object of the present application can be achieved. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, and other organic solvents.

For example, the carbonate compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), 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, 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, 1-fluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, At least one of trifluoromethyl ethylene carbonate.

The present application is not particularly limited as long as the object of the present application can be achieved. The packaging shell comprises at least one of an aluminum plastic film, an aluminum shell, a steel shell and a plastic shell. For example, the packaging shell may comprise an inner layer and an outer layer, the inner layer being sealingly connected to the barrier, and thus the material of the inner layer may comprise a polymeric material, thereby achieving a good sealing effect; meanwhile, the combination of the inner layer and the outer layer can effectively protect the internal structure of the electrochemical device. In the present application, the material of the inner layer is not particularly limited as long as the object of the present application can be achieved, and for example, the material of the inner layer includes at least one of polypropylene, polyester, parahydroxybenzaldehyde, polyamide, polyphenylene ether, polyurethane, and the like. In the present application, the material of the outer layer is not particularly limited as long as the object of the present application can be achieved, and for example, the material of the outer layer includes at least one of an aluminum foil, an aluminum oxide layer, a silicon nitride layer, and the like.

The thickness of the package is not particularly limited in this application as long as the object of the present application can be achieved. For example, the thickness of the casing is 60 μm to 500 μm, preferably 60 μm to 300 μm, and more preferably 60 μm to 200 μm, which can effectively protect the internal structure of the electrochemical device.

In the application, the seal thickness T (unit: mm) and the seal width W (unit: mm) of the seal area of the partition and the packaging shell meet the condition that T/W is more than or equal to 0.01 and less than or equal to 0.05. The ratio of T/W is in the range, so that the sealing of the battery can be ensured to be good, and the service life of the battery can be prolonged. In the present application, the seal thickness and the seal width are not particularly limited as long as the object of the present application can be achieved, and for example, the seal width is preferably 1mm to 7 mm.

The sealing connection mode of the partition board and the packaging shell is not particularly limited as long as the purpose of the present application can be achieved. For example, the sealing means includes one of hot pressing, glue sealing, and welding. In the present application, the hot pressing conditions are not particularly limited as long as the object of the present application can be achieved, and for example, the hot pressing temperature is 150 ℃ to 220 ℃ and the hot pressing pressure is 0.1Mpa to 0.6Mpa for the polypropylene inner layer material.

In some embodiments of the present application, the electrode assembly has a structure of a wound structure, and the electrode assembly includes a single or multiple tabs. The electrode assembly comprises a single-pole lug, and a positive pole lug and a negative pole lug are respectively led out from a positive pole piece and a negative pole piece. The electrode assembly comprises multiple tabs, wherein a positive tab and a negative tab are respectively led out from each circle of positive pole piece and negative pole piece, or a positive tab and a negative tab are respectively led out from two or more circles of positive pole pieces and negative pole pieces, and finally, the electrode assembly with a winding structure comprises multiple groups of positive tabs and negative tabs, and then tab leads are turned through transfer welding.

In some embodiments of the present application, the electrode assembly is a laminated structure, the electrode assembly includes multiple tabs, a positive tab and a negative tab may be respectively led out from each layer of positive electrode sheet and negative electrode sheet, and finally, the electrode assembly of the laminated structure includes multiple sets of positive tabs and negative tabs, and then tab leads are transferred by transfer welding.

In the present application, the distances D1-D6, W1, W1, O1 and O2 are measured by a micrometer along the X direction, Y direction or Z direction shown in fig. 1, and the average value is obtained by 10 times of measurement.

The present application also provides an electronic device comprising the electrochemical device provided herein. The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. For example, the display device includes, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handy cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, a lithium ion capacitor, and the like.

The method of preparing the electrochemical device of the present application is not particularly limited, and any method known in the art may be used, for example, in one embodiment, the present application may be prepared using the following preparation method:

(1) preparing a negative pole piece: and (3) mixing the negative active material and the solvent into slurry, and uniformly stirring. And uniformly coating the slurry on the negative pole piece and drying to obtain the single-side coated negative pole piece. And repeating the steps on the other surface of the negative pole piece to obtain the negative pole piece with double-coated surfaces. And then cutting the negative pole piece for later use. The coating thickness of the negative electrode active material on one surface was 70 μm.

(2) Preparing a positive pole piece: and (3) preparing the positive active material and the solvent into slurry, and uniformly stirring. And uniformly coating the slurry on the positive pole piece and drying to obtain the single-side coated positive pole piece. And repeating the steps on the other surface of the positive pole piece to obtain the positive pole piece with double-coated surfaces. And then cutting the positive pole piece for later use. The coating thickness of the positive electrode active material on one surface was 65 μm.

(3) Preparing an electrolyte: the lithium salt and the non-aqueous solvent were mixed and stirred uniformly to obtain an electrolyte containing a lithium salt at a concentration of 30%.

(4) Preparation of electrode assembly: the negative pole piece, the diaphragm and the positive pole piece are stacked and fixed together for standby, and each electrode assembly comprises a positive pole lug and a negative pole lug; repeating the above steps to obtain a plurality of electrode assemblies; the structure of the electrode assembly may be a winding structure or a lamination structure.

(5) A clapboard: any separator known in the art may be used.

(6) Assembling an electrode assembly: and placing the packaging shell in an assembly fixture, then arranging the electrode assembly and the separator at intervals, enabling the packaging shell to be adjacent to the electrode assembly, and finally sealing to obtain the assembled electrode assembly.

(7) Liquid injection and packaging: and respectively injecting electrolyte into the two cavities of the assembled electrode assembly, and leading all the tabs of the electrode assembly out of the aluminum plastic film for subsequent processing.

(8) Series connection: and welding and connecting the positive electrode lug of one electrode assembly and the negative electrode lug of the other electrode assembly together in a laser welding mode to realize series connection, and finishing the assembly of the battery.

The electrochemical device provided by the present application may include two electrode assemblies, or may include three or more electrode assemblies. The method of manufacturing an electrochemical device having two electrode assemblies or three or more electrode assemblies can be referred to the above-described method of manufacturing an electrochemical device. Electrochemical devices comprising three or more electrode assemblies are also within the scope of the present invention as defined in the claims.

The terms used in the present application are generally terms commonly used by those skilled in the art, and if they are not consistent with the commonly used terms, the terms in the present application shall control. In the present application, "%" and "parts" are based on weight unless otherwise specified.

The test method comprises the following steps:

testing the packaging strength of the series polar lug region:

the tab seal area portion was removed from the electrode assembly as sample 1;

cutting the sample 1 into a test strip with the width L of 8mm, ensuring that the whole sealing area is completely preserved by the test strip, and simultaneously ensuring that packaging shells at two sides of the sealing area are intact to obtain a sample 2;

tearing the packaging shells on the two sides at an angle of 180 degrees by using a high-speed rail tensile machine, so that the two packaging shells in the seal area are separated from each other;

and recording the stable tension F when the two packaging shells are separated, and calculating to obtain the packaging strength sigma which is F/L.

Discharge capacity after 50 charge-discharge cycles/first discharge capacity test:

in the test of comparative example 1, the test temperature was 25 ± 3 ℃, the lithium ion battery was charged to 4.2V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 4.2V, left to stand for 10min, then discharged to 3.0V at a current of 0.5C, the first discharge capacity was recorded as Q1D, the cycle was repeated 50 times in this way, and the discharge capacity at this time was recorded as Q50D, and then the discharge capacity/first discharge capacity retention ratio after 50 charge-discharge cycles was: η (%) ═ Q50D/Q1D × 100%;

in testing comparative examples 2 to 4 and examples 1 to 22, the test temperature was 25 ± 3 ℃, the lithium ion battery was charged to 8.4V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 8.4V, left to stand for 10min, then discharged to 6.0V at a current of 0.5C, the first discharge capacity was recorded as Q1D, and the cycle was repeated 50 times in this way, and the discharge capacity at this time was recorded as Q50D, and the discharge capacity/first discharge capacity retention ratio after 50 charge-discharge cycles was determined: η (%) ═ Q50D/Q1D × 100%.

And (3) testing the bending stability:

and (3) carrying out a 360-degree bending test on the two connected tabs, namely bending the tabs towards the X-Y surface (the X-Y surface is shown in figure 1) of the electrochemical device by taking the top seal area of the separator and the packaging shell as an axis until the connected tabs are attached to the X-Y surface, and marking as one-time bending. And then reversely bending the metal sheet for 360 degrees, attaching the metal sheet to the X-Y surface on the other side of the electrochemical device, and recording as secondary bending. Repeating the steps until the outer edge of the packaging of the tab glue and the packaging shell is cracked, and recording the bending times of the corresponding tab at the moment.

Testing the output voltage of the battery:

at the test temperature of 25 +/-3 ℃, the lithium ion battery is charged to Nx4.2V (N is the number of series electrode assemblies) at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of Nx4.2V, and kept stand for 1 hour, and the open-circuit voltage is measured to be the output voltage of the battery.

Testing the welding tension of the series tab:

the tab portion including the tab connection region was removed from the electrode assembly as a test sample. The whole connection area of the sample is completely preserved, and the lugs on two sides are intact. Tearing the tabs on two sides at an angle of 180 degrees by using a small tensile machine, so that the two tabs in the welding area are separated from each other; and recording the stable tension when the two lugs are separated, namely the welding tension.

And 2C temperature rise test of the charging tab:

charging to 4.45V at constant current of 0.5C and constant voltage of 4.45V to 0.025C at test temperature of 25 deg.C, and standing for 5 min. Then discharged to 3.0V at 0.5C and left to stand for 5 min. The temperature of the tab at this time was T1 as measured using a multi-way thermometer. Charging to 4.45V at a constant current of 2C, and testing the temperature of the lug at the moment to be T2 by using a multi-path temperature measuring instrument. The temperature rise Δ T of the 2C charging tab is T2-T1.

Example 1

(1) Preparing a negative pole piece: mixing the negative active material artificial graphite, conductive carbon black (Super P) and Styrene Butadiene Rubber (SBR) according to the weight ratio of 96:1.5:2.5, adding deionized water as a solvent, preparing slurry with the solid content of 70 wt%, and uniformly stirring. And uniformly coating the slurry on one surface of a negative current collector copper foil with the thickness of 10 mu m, and drying at 110 ℃ to obtain the negative pole piece with the coating thickness of 150 mu m and the single surface coated with the negative active material layer. And repeating the steps on the other surface of the negative pole piece to obtain the negative pole piece with the negative active material layer coated on the two surfaces. Then, the negative electrode plate is cut into a size of 41mm × 61mm for standby.

(2) Preparing a positive pole piece: the positive electrode active material lithium cobaltate (LiCoO)₂) Mixing conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) according to the weight ratio of 97.5:1.0:1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75 wt%, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil of the positive current collector with the thickness of 12 mu m, and drying at 90 ℃ to obtain the positive pole piece with the positive active material layer with the thickness of 100 mu m. And repeating the steps on the other surface of the aluminum foil of the positive current collector to obtain the positive pole piece with the positive active material layer coated on the two surfaces. Then, the positive pole piece is cut into 38mm × 58mm for standby.

(3) Preparing an electrolyte: in a dry argon atmosphere, organic solvents of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC: EMC: DEC: 30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF) was added to the organic solvent₆) Dissolving and mixing uniformly to obtain the electrolyte with the concentration of lithium salt of 1.15 mol/L.

(4) Preparation of electrode assemblies a and B: the diaphragm, the double-sided coated negative pole piece, the diaphragm and the double-sided coated positive pole piece are sequentially stacked to form a lamination, and then four corners of the whole lamination structure are fixed for later use. Each electrode assembly comprises a positive electrode tab and a negative electrode tab, wherein the positive electrode tab is aluminum (Al) and the negative electrode tab is nickel (Ni), the two tabs are arranged side by side, the thickness D4 of the tabs is 0.3mm, and the width W1 of the tabs is 5 mm; the separator was a Polyethylene (PE) film with a thickness of 15 μm.

(5) Preparing a separator: uniformly dispersing polypropylene (PP, the melting point is 140 ℃) serving as a packaging layer material into N-methylpyrrolidone (NMP) serving as a dispersing agent to prepare PP suspension; respectively coating PP turbid liquid on two sides of a Polyimide (PI) film with the thickness of 15 mu m by using a glue spreader; then drying at 130 ℃ to remove the dispersant NMP in the suspension, thus completing the preparation of the separator. Wherein the thickness of the separator is 15 μm.

(6) Assembly of electrode assembly a: placing the aluminum-plastic film (with the thickness of 150 mu m) formed by punching a pit into an assembly fixture, enabling the pit to face upwards, placing an electrode assembly A into the pit, enabling a diaphragm to face upwards, arranging tab glue with the width of 11mm in an area corresponding to a tab of the electrode assembly A at the edge of the aluminum-plastic film, then placing a separator on the electrode assembly A, enabling the edges to be aligned, and applying external force to compress the separator to obtain an assembled semi-finished product. The distance D1 between the upper edge of the tab glue and the upper edge of the packaging shell is 1mm, the shoulder width D2 of the tab glue is 3mm, and the thickness D3 of the tab glue is 0.2 mm.

(7) Assembly of electrode assembly B: and placing the assembled semi-finished product in an assembling clamp with one side of the partition upward and the diaphragm surface of the electrode assembly B downward on the partition so that the edges are aligned, applying external force to compress the assembled semi-finished product, covering the other hole-punched aluminum plastic film with the pit surface downward on the electrode assembly B, arranging tab glue with the width of 11mm in an area corresponding to the tab of the electrode assembly B at the edge of the aluminum plastic film, and performing heat sealing on the periphery by adopting a hot pressing mode to obtain the assembled electrode assembly. The distance D1 between the upper edge of the tab glue and the upper edge of the packaging shell is 1mm, the shoulder width D2 of the tab glue is 3mm, and the thickness D3 of the tab glue is 0.2 mm.

(8) Liquid injection and packaging: and respectively injecting electrolyte into each cavity of the assembled electrode assembly, and leading all the lugs of the electrode assemblies A and B out of the aluminum plastic film. The width of the overlapping area of the negative electrode tab of the electrode assembly A and the positive electrode tab of the electrode assembly B is 4.75mm, and the width of the overlapping area of the negative electrode tab of the electrode assembly A and the positive electrode tab of the electrode assembly B is 10.67 mm.

(9) Series connection: and welding and connecting the negative pole lug of the electrode assembly A and the positive pole lug of the electrode assembly B together in a laser welding mode to realize series connection, and finishing the assembly of the battery. Wherein the content of the first and second substances,the area S1 of the connection region is 20mm²The distance D5 between the two connected tabs is 3mm, and the distance D6 between the connecting area and the aluminum-plastic film is 5 mm.

Example 2

The width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B was 2.5mm, and the width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B by tab glue was 5.61mm, which were the same as in example 1.

Example 3

The same as example 1 except that the distance D1 between the upper edge of the tab adhesive and the upper edge of the pack case was 5 mm.

Example 4

The width of the tab glue is 8mm, the shoulder width D2 of the tab glue is 1.5mm, and the rest is the same as that of the embodiment 1.

Example 5

The same as example 1 except that the thickness D3 of the tab paste was 3 mm.

Example 6

The same as example 1 except that the thickness D4 of the tab was 2 mm.

Example 7

The same as example 1 except that the width W1 of the tab was 10 mm.

Example 8

The same as example 1 except that the distance D5 between the two tabs to be connected was 6 mm.

Example 9

The same as example 1 except that the distance D6 between the connection region and the aluminum plastic film was 30 mm.

Example 10

The same as example 1 except that the thickness of the separator was 200. mu.m.

Example 11

The width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B was 3mm, and the width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B by tab glue was 6.6mm, and the rest was the same as in example 1.

Example 12

The same as example 1 except that the distance D5 between the two tabs to be connected was 1 mm.

Example 13

The same as example 1, except that the tab shoulder width D2 was 1.5mm, and the distance D6 between the connection region and the aluminum plastic film was 3 mm.

Example 14

The same as example 1, except that the distance D5 between the two tabs to be connected was 6mm, and the distance D6 between the connection region and the aluminum plastic film was 4 mm.

Example 15

Except that the area S1 of the connecting region is 4mm²The electrode assembly 0.2C rated capacity was 10A, the maximum discharge rate was 2C, and the rest was the same as example 3. Wherein the current carrying capacity per unit area of the connecting region is 5A/mm²。

Example 16

Except that the area S1 of the connecting region is 3mm²The maximum discharge rate was 3C, and the rest was the same as in example 15.

Example 17

Except that the area S1 of the connecting region is 10mm²The electrode assembly 0.2C rated capacity was 50A, the rest being the same as in example 15.

Example 18

Preparing an electrode assembly C according to the step (4) of example 1; when the electrode assembly is packaged, the diaphragm surface of the electrode assembly B faces downwards, the electrode assembly B is placed on the separator, the edges are aligned, the separator is arranged on the electrode assembly B after the electrode assembly B is pressed by applying external force, the diaphragm surface of the electrode assembly C faces downwards, the electrode assembly C is placed on the separator, the edges are aligned, and the electrode assembly C is pressed by applying external force; and covering the other pit surface of the aluminum-plastic film formed by punching the pit downwards on the electrode assembly C, arranging a tab glue with the width of 11mm in the area corresponding to the tab of the electrode assembly C at the edge of the aluminum-plastic film, and performing heat sealing on the periphery by adopting a hot pressing mode to obtain an assembled electrode assembly.

And leading all the tabs of the electrode assembly C out of the aluminum plastic film, and welding and connecting the negative electrode tab of the electrode assembly B and the positive electrode tab of the electrode assembly C together in a laser welding manner to realize series connection, thus finishing the assembly of the battery.

The rest is the same as in example 15.

Example 19

The same as example 15 was repeated, except that the positive and negative electrode tabs of the electrode assemblies a and B were protruded out of the pack case in opposite directions, respectively.

Example 20

(1) Preparing a negative pole piece: the negative electrode piece was cut into a size of 41mm × 550mm for use, and the rest was the same as in example 1.

(2) Preparing a positive pole piece: the positive electrode sheet was cut into a size of 35mm × 547mm for use, and the rest was the same as in example 1.

(4) Preparation of electrode assemblies a and B: and (3) stacking the diaphragm, the double-sided coated negative pole piece, the diaphragm and the double-sided coated positive pole piece, and then winding from one end to form a wound electrode assembly. Each electrode assembly comprises a positive electrode tab and a negative electrode tab, the two tabs are arranged side by side, the thickness D4 of the tabs is 0.3mm, and the width W1 of the tabs is 5 mm; the separator was a Polyethylene (PE) film having a thickness of 15 μm.

(6) Assembly of electrode assembly a: and (2) placing the aluminum-plastic film (with the thickness of 150 mu m) formed by punching the pits into an assembly fixture, enabling the pit surface to face upwards, placing an electrode assembly A into the pits, then placing a separator on the electrode assembly A, arranging tab glue with the width of 11mm in the area corresponding to the tabs of an electrode assembly B at the edge of the aluminum-plastic film, aligning the edges, and applying external force to compress the tab glue to obtain an assembled semi-finished product. The distance D1 between the upper edge of the tab glue and the upper edge of the packaging shell is 5mm, the shoulder width D2 of the tab glue is 3mm, and the thickness D3 of the tab glue is 0.2 mm.

(7) Assembly of electrode assembly B: and placing the assembled semi-finished product into an assembling clamp with the separator facing upwards, placing an electrode assembly B on the separator, aligning the edges, applying external force to compress the assembled semi-finished product, covering the other hole face of the aluminum plastic film subjected to hole punching forming downwards on the electrode assembly B, arranging tab glue with the width of 11mm in an area corresponding to a tab of the electrode assembly B at the edge of the aluminum plastic film, and performing heat sealing on the periphery by adopting a hot pressing mode to obtain the assembled electrode assembly. Wherein, the distance D1 between the upper edge of the tab glue and the upper edge of the packaging shell is 5mm, the shoulder width D2 of the tab glue is 3mm, and the thickness D3 of the tab glue is 0.2 mm.

(9) The electrode assemblies are connected in series: and welding and connecting the negative pole lug of the electrode assembly A and the positive pole lug of the electrode assembly B together in a laser welding mode to realize series connection, and finishing the assembly of the battery. Wherein the area S1 of the connection region is 30mm²The distance D5 between the two tabs connected by welding is 3mm, and the distance D6 between the connecting area and the aluminum-plastic film is 5 mm.

Comparative example 1

And placing the aluminum-plastic film subjected to pit punching forming into an assembly fixture, enabling the pit surface to face upwards, placing an electrode assembly A into the pit, enabling the diaphragm surface to face upwards, then placing an electrode assembly B onto the electrode assembly A, aligning the edges, applying external force to compress, then covering the other aluminum-plastic film subjected to pit punching forming downwards onto the electrode assembly B, and performing heat sealing on the periphery by adopting a hot pressing mode to obtain an assembled electrode assembly. Wherein, the shoulder width D2 of the tab glue is 3mm, the thickness D3 of the tab glue is 0.2mm, the distance D1 between the edge of the tab glue and the upper edge of the packaging shell is 1mm, the distance between two connected tabs is 3mm, the thickness D4 of the tab is 0.3mm, and the rest is the same as that of the embodiment 1.

Comparative example 2

The width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B was 1mm, and the width of the overlapping region of the negative electrode tab of the electrode assembly a and the positive electrode tab of the electrode assembly B by tab glue was 2.31mm, and the rest was the same as in example 1.

Comparative example 3

The same as example 1 except that the distance D5 between the two tabs to be connected was 1mm, and the distance D6 between the connection region and the aluminum plastic film was 1 mm.

Comparative example 4

The same as example 1 except that the distance D5 between the two tabs to be connected was 6mm, and the distance D6 between the connection region and the aluminum plastic film was 3.5 mm.

The data and test results for each example and comparative example are shown in tables 1 and 2.

As can be seen from examples 1 to 14 and comparative examples 2 to 3 in table 1, the bending resistance of the electrochemical device of the present application is significantly improved as the ratio of the overlapping width of the two tabs to be connected to any tab width and the ratio of the width of the tab glue overlapping area to any tab glue width are increased.

As can be seen from examples 1 to 14 and comparative example 2 in table 1, the joint region encapsulation strength of the electrochemical device of the present application was significantly improved, and the discharge capacity after 50 cycles/first discharge capacity was improved.

As can be seen from examples 1 to 14 and comparative examples 3 and 4 in table 1, the bending stability of the electrochemical device of the present application was greatly improved as long as the value of D6, and the value of D5/D6 were within the range of the present application.

As can be seen from examples 1 to 14 and comparative example 4 in Table 1, if the ratio of D5/D6 is within the range of the present application, the bending stability of the electrochemical device is improved, thereby improving the reliability of the use of the electrochemical device.

As can be seen from examples 15 to 20 and comparative examples 2 and 3 in table 2, the welding tension of the connection region of the electrochemical device of the present application was significantly increased, the output voltage was not substantially changed, and the temperature rise of the 2C charging tab was decreased, indicating that the electrochemical device of the present application had good connection reliability and use reliability.

As can be seen from examples 15 to 20 and comparative examples 3 and 4 in table 2, if the ratio of D5/D6 is within the range of the present application, the welding tension in the welded connection region in the electrochemical device is significantly increased, and the temperature rise of the 2C charging tab is reduced, thereby improving the reliability of the electrochemical device.

The packaging strength and the bending stability of an electrochemical device are generally influenced by the proportion alpha of the overlapping width of two connected tabs in the width of any tab and the proportion beta of the width of the tab glue overlapping area in the width of any tab glue; the area S1 of the joint region generally affects the joint strength of the joint region and the temperature rise of the tab; the design and control of the relative positions of the two tabs to be connected generally affect the connection reliability between the adjacent electrode assemblies and the packaging reliability of the electrochemical device, i.e., are accomplished by adjusting the distance sizes of D1-D6. As can be seen from examples 1 to 20, the obtained electrochemical device achieves not only an improvement in output voltage but also an improvement in connection reliability and packaging reliability, as long as the above parameters are within the range of the present application, and has excellent industrial applicability.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An electrochemical device comprising at least two electrode assemblies and a package case, the electrode assemblies being respectively disposed in separate cavities within the package case;

the tab width W1 is the width of any one of the two connected tabs along the length direction X of the seal at the outer edge of the seal of the packaging shell when viewed along the thickness direction Z of the seal;

the distance between the two connected tabs at the outer edge of the package seal is D5; the two connected tabs are provided with a connecting area, and the length of the tab between the connecting area and the outer edge of the packaging shell seal is D6; the relationship between D5 and D6 satisfies: 0< D5/D6 is less than or equal to 1.7.

2. The electrochemical device as claimed in claim 1, wherein each of the two connected tabs is provided with tab glue, the tab glue provided on the tab has a tab glue width exceeding both sides of the tab along the length direction X of the seal at the outer edge of the seal of the package casing, and the ratio of the tab glue shoulder width D2 to the tab width W1 is D2/W1 ≥ 1/60;

3. The electrochemical device according to claim 2, wherein the orthographic projection of the tab glue on the two connected tabs along the seal thickness direction Z has a tab glue overlapping area, and the proportion of the tab glue overlapping width O2 to any tab glue width W2 is 40% < β ≦ 100%;

4. The electrochemical device of claim 1, wherein 3mm ≦ D6 ≦ 30 mm.

5. The electrochemical device of claim 1, wherein 0.1mm < D5 ≦ (H1+ H2)/2+5mm, wherein H1 and H2 are thicknesses of the two connection electrode assemblies, respectively.

6. The electrochemical device according to claim 1, wherein the area S1 of the connection region is 1mm²To 200mm²。

7. The electrochemical device according to claim 2, wherein the tab jelly is spaced apart from the upper edge of the pack case in the seal width direction Y by a distance of 0.2mm or more and D1 or less and 5mm or less, the tab jelly has a thickness of 0.1mm or more and D3 or more and 3mm or less, and the tab has a thickness of 0.2mm or more and D4 or more and 5mm or less in a direction away from the electrode assembly.

8. The electrochemical device of claim 1, wherein α is 50% to 100%.

9. The electrochemical device of claim 1, wherein the two tabs that are connected are two tabs of opposite polarity.

10. The electrochemical device according to claim 1, wherein the electrode assembly has tabs protruding from the pack case from different directions.

11. The electrochemical device according to claim 1, further comprising a separator between the electrode assemblies, wherein a thickness of the separator is 2 μm to 100 μm.

12. The electrochemical device according to claim 1, wherein the structure of the electrode assembly includes at least one of a wound structure and a laminated structure.

13. The electrochemical device of claim 1, wherein the packaging case comprises at least one of an aluminum plastic film, an aluminum case, a steel case, and a plastic case.

14. An electronic device comprising the electrochemical device according to any one of claims 1 to 13.