TW201521264A - Electrode assembly and electrochemical device including the same - Google Patents

Abstract

Disclosed is a technology for preventing electrodes in a secondary battery from being short-circuited with each other. An electrode assembly includes a cathode and anode of which a cathode collector and anode collector are coated with a cathode active material and anode active material, respectively, and a separator disposed between the cathode and the anode. An insulation layer is disposed on a tab part of the cathode collector constituting the cathode. Thus, an insulation layer may be disposed on an end (a tab part) of the cathode collector that is used as a tab of the cathode electrode in the structure of the electrode assembly to prevent the cathode from being physically short-circuited with the anode in the sequentially stacked structure of cathode/separator/anode.

Description

Electrode group and electrochemical device containing the same

The present invention relates to a technique for preventing short-circuiting of electrodes in a secondary battery to each other.

Recently, lithium secondary batteries that are rechargeable/dischargeable, light in weight, and have high energy density and high output density have been widely used as energy sources for wireless mobile devices. Lithium secondary batteries are also attracting attention as power sources for hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery electric vehicles (BEV) and electric vehicles (EV). Developed to address limitations such as air pollution and greenhouse gases (caused by existing internal combustion engine vehicles using diesel fuel (such as gasoline and diesel vehicles)).

Lithium secondary batteries are classified into a lithium ion battery using a liquid electrolyte and a lithium polymer battery using a polymer electrolyte by electrode type. Further, the lithium secondary battery is classified into a cylindrical type, a prism type, or a capsule type lithium secondary battery according to the shape of the sleeve accommodating the electrode group.

Wherein the capsule type lithium secondary battery having the outer portion of the capsule includes gold A genus layer (foil) and a multilayered synthetic resin film applied to the top and bottom surfaces of the metal layer. Therefore, the capsule type lithium secondary battery can be developed into a light lithium secondary battery and changed into various shapes, which can significantly reduce the weight of the battery compared to a cylindrical or prismatic lithium secondary battery using a metal container. Therefore.

The outer portion of the bladder includes upper and lower outer portions which are formed by folding the intermediate portion of one side of the rectangular sleeve in the longitudinal direction. Here, a pressurization process may be performed on the lower outer portion to form a space portion accommodating the electrode group. Among the structures of the various electrode groups, the cathode, the separator, and the mostly anode-shaped stack are housed in the space portion of the lower outer portion. Thereafter, the electrolyte is injected, and the edge of the space portion surrounding the lower outer portion is tightly joined to the edge of the upper outer portion corresponding to the lower outer portion. Thereafter, the closely joined portions are heat welded to form a sealed capsule type lithium secondary battery.

Fig. 1 is an enlarged perspective view showing a general structure of a representative capsule type lithium secondary battery according to the related art.

Referring to Fig. 1, a capsule type lithium secondary battery 1 includes an electrode group 10, electrode tabs 31 and 32 extending from the electrode group 10, electrode leads 51 and 52 soldered to the electrode tabs 31 and 32, and an electrode group 1 accommodating the electrode group 1. Battery case 20.

The electrode assembly 10 can be a power generating device in which a cathode and an anode are continuously stacked with a separator therebetween. The electrode group 10 has a stacked or stacked/folded structure. The electrode tabs 31 and 32 extend from the electrode plates of the electrode group 10, respectively. The electrode wires 51 and 52 are respectively electrically connected to a plurality of electrode tabs 31 and 32 extending from the electrode plate by soldering. Here, a part of each of the electrode wires 51 and 52 is exposed outside the battery can 20. with At this time, the insulating film 53 can be bonded to a part of each of the top and bottom surfaces of the electrode wires 51 and 52 to improve the sealing property and ensure electrical isolation from the battery can 20.

In addition, a plurality of cathode and anode tabs 31 and 32 are integrally coupled to form a welded portion, respectively. Therefore, the inner upper end of the battery can 20 is spaced apart from the top surface of the electrode group 10 by a predetermined distance, and the tabs 31 and 32 of the welded portion are each bent into a V shape (hereinafter, the coupling portion of the electrode tab and the electrode wire is referred to as Into V parts 41 and 42). The battery can 20 is formed of an aluminum laminated sheet and provides a space for accommodating the electrode group 10. The battery can 20 also has a full capsule shape. After the electrode group 10 is housed in the accommodating portion of the battery can 20 and after the electrolyte (not shown) is injected, the peripheral surface of the upper and lower laminated sheets of the battery can 20 is thermally welded to manufacture a secondary battery.

Fig. 2 is a conceptual diagram for explaining the structural limitation of the above electrode group.

As shown in Fig. 2, in the specific structure of the electrode group 10, the cathode and the anode are stacked. Further, the electrode 10 includes electrode tabs 31 and 32 connected to a collector constituting a cathode and an anode. Here, in FIG. 2, the portion indicated by the aluminum (Al) foil 31 is the cathode tab 31, and the portion indicated by the copper (Cu) foil is the anode tab 32. Specifically, in the electrode group, the cathode coated with the cathode active material on the collector and the anode coated with the anode active material on the collector are stacked on each other. A separator for avoiding a physical short circuit between the cathode and the anode is also interposed between the cathode and the anode. Here, to reduce the risk of a physical short circuit between the cathode and the anode in the normal electrode group, the anode size is larger than the cathode. However, because the separator shrinks in a high temperature environment, Therefore, a physical short circuit between the cathode and the anode often occurs.

One aspect of the present invention provides a secondary battery in which an insulating layer is located on a cathode collector end (a tab component) as a tab of a cathode in an electrode group structure to prevent a cathode and a continuous stack structure at the cathode/separator/anode The physical short circuit of the anode in the middle.

According to another aspect of the present invention, there is provided an electrode assembly comprising: a cathode and an anode, wherein a cathode collector and an anode collector are respectively coated with a cathode active material and an anode active material; and disposed between the cathode and the anode a separator in which an insulating layer is located on a tab component of the cathode collector constituting the cathode. Therefore, in the continuous stack structure of the cathode/separator/anode, a physical short circuit between the cathode and the anode can be prevented.

1‧‧‧Capsule lithium secondary battery

10‧‧‧electrode group

20‧‧‧ battery case

31‧‧‧electrode ear

32‧‧‧electrode ear

41‧‧‧ into part V

42‧‧‧ into part V

51‧‧‧Electrode wire

52‧‧‧Electrode wire

53‧‧‧Insulation film

110‧‧‧Cathode collector

120‧‧‧Cathodic active materials

130‧‧‧ separator

140‧‧‧Anode active material

150‧‧‧Anode collector

160‧‧‧Insulation

122‧‧‧ cathode

142‧‧‧Anode

T1‧‧‧ total length

T2‧‧‧ exposed part

T3‧‧‧ non-overlapping areas

The above and other aspects, features and other advantages of the present invention will become more apparent from the detailed description of the accompanying drawings in which <RTIgt; A conceptual diagram explaining the limitation of the structure of the secondary battery; FIG. 3 is a cross-sectional view illustrating the structure of the electrode assembly according to the present invention; and FIG. 4 is a view for forming an insulating layer on the tab member of the cathode collector according to the present invention. Plan of the method.

Exemplary embodiments of the present invention will now be described in detail with reference to the drawings. In the description of the drawings, like reference numerals refer to like elements, and, Although the terms "first" and "second" are used to describe various components, the components are not limited to these terms. These terms are only used to distinguish the components from each other.

3 is a cross-sectional view for explaining the structure of an electrode group according to the present invention, and FIG. 4 is a plan view showing a method for forming an insulating layer on a tab member of a cathode collector according to the present invention.

Referring to Figures 3 and 4, an electrode assembly in accordance with the present invention can include a cathode 122 coated by a cathode collector 110 via a cathode active material 120, an anode 142 coated with an anode collector 150 via an anode active material 140, and placed at the cathode and anode. An intermediate separator 130, and an insulating layer 160 on the tab members of the cathode collector 110 constituting the cathode 122.

In particular, the insulating layer 160 according to the present invention is located between the cathode collector 110 and the separator 130 and may be partially overlapped with a region coated with the anode active material 140. That is, since the size of the anode is larger than the cathode, the non-overlapping region T3 may exist between the anode and the cathode. In general, since the short circuit between the electrodes occurs due to the non-overlapping region T3, the insulating layer 160 may be located on the non-overlapping region T3.

That is, the position of the insulating layer 160 may partially overlap with the region coated by the anode active material 140. Basically, the insulating layer 160 is attached to the end of the region coated by the cathode active material 120. The position of the insulating layer 160 The exposed portion T2 defined by exposing the ends of the tab members can also be formed. Further, the width (region T3) of the insulating layer 160 is from about 1 mm to about 20 mm. In this case, the insulating layer 160 itself has a thickness of about 1 micron to a silt of 100 micrometers. The total length T1 of the exposed portion T2 and the insulating layer 160 may be from about 20 mm to about 30 mm.

4 is a plan view of the cathode 122 in a state where the cathode active material 120 in FIG. 3 is applied to the cathode collector 110.

As shown in FIG. 3, the method of forming the insulating layer 160 may be a method in which an insulating material is applied to the end of the cathode collector 110 region coated with the cathode active material 120 in the length direction of the collector.

Alternatively, as shown in FIG. 4, the method of forming the insulating layer 160 may be performed by applying an insulating material containing at least one ceramic material. For example, the insulating layer 160 may be formed by applying at least one material selected from the group consisting of titanium dioxide, calcium carbonate, and barium sulfate or a mixture of at least two materials, or from about 10% by weight to about 90 by application. The weight % is formed by a solution or lacquer selected from the group consisting of titanium dioxide, calcium carbonate, and barium sulfate.

Further, the insulating layer 160 can be obtained by bonding and applying a polymer film or emulsion having a weight average molecular weight of about 200,000 or less to the tab member. In this case, the polymer film is selected from the group consisting of polyacrylate, polystyrene, polyacrylic acid, polyacrylonitrile, polyethylene, polypropylene, polyimide, polyurethane, and polypyridyl acid. At least one material of the group consisting of diesters is formed. Alternatively, the polymer layer is formed from a polymer based on styrene-butadiene rubber (SBR).

That is, the insulating layer 160 according to the present invention can be obtained by using various methods such as spin coating, printing, spraying, and embossing.

An experimental example for confirming whether or not a contact defect occurs in a secondary battery including an electrode lead according to the present invention will be described below. The electrode group according to the present invention can constitute one of a jelly roll type, a stacked type, and a stacked/folded type secondary battery. Hereinafter, specific embodiments of the present invention will be described in more detail. It is to be noted that the following specific embodiments are not intended to limit the scope of the claims

{Specific embodiment}

At the top of the cathode collector, the electrode assembly was fabricated by using materials and methods known in the art, but the insulating layer was formed to have a width of about 10 mm and a thickness of about 10 from the end of the cathode active material.

In this embodiment, the insulating layer is formed by using a solution containing a polymer which is a modified SBR-based polymer (including a small amount selected from the group consisting of acrylic acid, acrylonitrile, and ethyl hexyl acrylate). At least one of the group consisting of butyl acrylate and styrene as a main component is formed or a solution in which titanium dioxide is dispersed in water or methanol is formed. Thereafter, using this insulating layer, 100 electrode groups were fabricated. Each of the prepared electrode groups was placed in a housing portion of the battery can. Thereafter, a plurality of electrode tabs extend from the collector of the electrode set to the tabs and the wire portions are welded to form a V portion. Thereafter, the electrolyte was injected, and the outer surface of the battery case in which the upper laminated sheet and the lower laminated sheet were in contact with each other was heat-welded to seal the battery can, thereby co-manufacturing 100 bladder-type secondary batteries.

{Comparative example}

The capsule type secondary battery was manufactured by the same method as the above specific example, but the insulating layer was omitted.

{Experimental example}

The test results obtained by exposing the batteries manufactured in the specific examples and the comparative examples to temperatures of about 100 ° C, 150 ° C, and 200 ° C are shown in Table 1 below.

In this experimental example, the above test was repeated on 100 batteries to determine whether or not the anode was short-circuited.

In this test, not all of the 100 secondary batteries were physically short-circuited, each of which was equipped with an insulating layer, and the cathode structure of the present invention was applied to the other. However, it can be seen that the defect rate occurring in the general comparative example is about 13%.

Hereinafter, specific materials and structural features constituting the individual components of the electrode group in which the above-described insulating layer is assembled according to the present invention will be described.

Cathode structure

The electrodes formed on the base unit body of the present invention are classified into a cathode and an anode. The cathode and the anode are coupled to each other with a separator interposed therebetween to fabricate an electrode. For example, the cathode can be fabricated by applying a mixture of a cathode active material, a conductive material, and a binder to a cathode collector and then performing a drying and pressurizing procedure on a cathode collector to which the mixture has been applied. Fillers may be added to the mixture if necessary. This structure can be in the form of a sheet and applied later to be processed in the shape of a sheet packaged on a carrier roll.

[cathode collector]

Typically, cathode collectors are typically formed to a thickness of from about 3 microns to about 500 microns. This cathode collector is not particularly limited as long as it has high conductivity and does not cause adverse chemical changes in the battery. The cathode collector can be fabricated, for example, from stainless steel, aluminum, nickel, titanium, burnt carbon, or aluminum or stainless steel surface treated with one of carbon, nickel, titanium, silver, and the like. The collector may have a non-uniform surface to improve the bonding strength of the cathode active material and may have any of various shapes such as a film, a sheet, a foil, a mesh, a porous body, a foam, a non-woven body, and the like. In accordance with a previous embodiment of the present invention, the electrode tabs may be formed of the same material as the cathode collector.

[cathode active material]

In the case of a lithium secondary battery, the cathode active material may include a layered compound such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), or a compound substituted with at least one transition metal; lithium manganese oxide , such as the chemical formula Li _1+x Mn _2-x O ₄ (where x ranges from about 0 to about 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium Oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ ; nickel lithiated nickel oxides, represented by the chemical formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ge, and x range from about 0.01 to about 0.3); lithium manganese mis-oxides, which have the chemical formula LiMn _2-x M _x O ₂ (where M = Co , Ni, Fe, Cr, Zn, or Ta, and x ranges from about 0.01 to about 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _4. A lithium which is a part of the chemical formula is substituted with an alkaline earth metal ion; a disulfide compound; or a complex oxide formed of Fe ₂ (MoO ₄ ) ₃ , but the invention is not limited thereto.

The conductive material is usually added in an amount of from about 1 to about 50% by weight based on the total weight of the mixture including the cathode active material. Any conductive material can be used without particular limitation as long as it has a suitable conductivity and does not cause adverse chemical changes in the battery. For example, the conductive material may include a conductive material such as graphite, such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, And thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate A conductive oxide such as titanium oxide; or a polyphenylene derivative.

The binder is a component that assists the bonding between the active material and the conductive material and the bond between the active material and the collector. Including the cathode The binder is usually added in an amount of from about 1 to about 50% by weight based on the total weight of the compound of the active material. Examples of the binder include polydifluoroethylene, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, ethylene-propylene-diene trimer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

The filler is selectively used to inhibit the expansion of the anode component. The filler is not particularly limited as long as it is a fibrous material which does not cause adverse chemical changes of the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers.

Anode structure

The anode is formed by applying, drying, and pressurizing the anode active material on the anode collector. Conductive materials, binders, and fillers may be further selectively added to the anode as needed. This structure can be in the form of a sheet and applied later to be processed in the shape of a sheet packaged on a carrier roll.

[Anode collector]

The anode collector is typically formed to a thickness of from about 3 microns to about 500 microns. The anode collector is not particularly limited as long as it is electrically conductive and does not cause adverse chemical changes in the battery. The anode collector can be made of, for example, copper, stainless steel, aluminum, nickel, titanium, burnt carbon, or copper stainless steel, aluminum-cadmium surface treated with one of carbon, nickel, titanium, silver, and the like. Alloys and the like. Also similar to cathode collector, anode collector It may have a fine rough surface to improve the bonding strength with the anode active material. The anode collector can have various shapes such as a film, a sheet, a foil, a mesh, a porous body, a foam, a non-woven body, and the like. In accordance with a previous embodiment of the present invention, the electrode tabs may be formed of the same material as the anode collector.

[Anode active material]

For example, the anode active material may include: carbon such as hard carbon or graphite-based carbon; and a misaligned metal oxide such as Li _x Fe ₂ O ₃ (0) x 1), Li _x WO ₂ (0 x 1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, or Ge; Me': Al, B, P, Si, Group I, II, and III elements, or halogen; <x 1;1 y 3; and 1 z 8); lithium metal; lithium alloy; bismuth-based alloy; tin-based alloy; metal oxides such as SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and Bi ₂ O ₅ ; conductive polymers such as polyacetylene; and Li-Co-Ni Based on materials.

[separator]

The separator according to the present invention can be obtained by simply laminating the base unit body by a simple lamination procedure regardless of the folding or winding process. In particular, by using heat, the separator and the cathode and the anode in the laminate can be obtained by melting the separator sheet itself into the laminate such that the separator is adhered and fixed to the cathode and the anode. Therefore, continue to maintain pressure to ensure The electrode is in contact with the stable surface of the separator sheet.

The material of the separator sheet or separator that is not particularly placed between the cathode and the anode of the battery is as long as the separator sheet or the separator has a porous structure in which ions can move. The separator and separator sheets may or may not be formed of the same material.

As the separator or separator sheet, for example, an ion-permeable and mechanically high insulating film can be used. The separator or separator sheet has a pore diameter of from about 0.01 microns to about 10 microns and a thickness of from about 5 microns to about 300 microns. For example, flaky or non-woven fabrics made of olefin polymers (such as polypropylene), glass fibers or polyethylene are chemically resistant and hydrophobic; as separators or separator sheets. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte can also function as a separator. The separator may be a polyethylene film, a polypropylene film, a multilayer film obtained by combining these films, or a polymer electrolyte or a gel-type polymer electrolyte (such as polydifluoroethylene, polyethylene oxide, poly A polymer film of acrylonitrile or a polydifluoroethylene hexafluoropropylene copolymer.

The separator may have an adhesive function by thermally bonding to constitute a base unit battery. The separator sheet also (but not necessarily) has an adhesive function.

The electrode assembly according to the present invention can be applied to an electrochemical cell that manufactures electricity by using an electrochemical reaction between the cathode and the anode. Representative examples of electrochemical cells include advanced capacitors, supercapacitors, secondary batteries, fuel cells, all kinds of perceptrons, machinery for electrolysis, and electrochemical reactors. Among them, electrochemical cells are mainly used for secondary batteries.

This secondary battery may have a structure in which a chargeable/dischargeable electrode group is built in a battery case in a state where the electrode group is immersed in an ion-containing electrolyte. For example, the secondary battery may be a lithium secondary battery.

In recent years, lithium secondary batteries have received more attention in terms of power sources as large-scale devices and small-sized devices. When a lithium secondary battery is applied to the aforementioned field, the lithium secondary battery can have a very small weight. In order to reduce the weight of the lithium secondary battery, the electrode group can be built in a capsule shell made of an aluminum laminated sheet. Since the lithium secondary battery is known to the art, a detailed description thereof will not be provided.

Further, as described above, when the secondary battery is used as a power source for the medium-large size device, the secondary battery has a structure in which, even if it is used for a long period of time, the damage of the operational performance is most suppressed, achieving an excellent life cycle, and It can be manufactured in large quantities at low cost. Here, a secondary battery including the electrode group according to the present invention can be used for using a secondary battery as a large-sized battery module.

In the case of a battery pack including a battery module having a plurality of secondary batteries, the battery pack can be used as a power tool, an electric vehicle (EV) (including a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle). At least one power source (PHEV), E-bike, E-motorcycle, electric golf cart, electric truck, and electric commercial vehicle.

The configuration of the medium-large size battery module provides high output and large capacity by a plurality of unit cells connected in series or in series-parallel connection. However, since this configuration is known to the art, a detailed description thereof will not be made.

According to the invention, an insulating layer is located at the end of the cathode collector On the (earer part), the tabs of the cathode in the electrode assembly structure are used to prevent physical shorting of the cathode to the anode in the continuous stack structure of the cathode/separator/anode.

The present invention has been shown and described with respect to the embodiments of the invention, and it is obvious that modifications and changes may be made without departing from the spirit and scope of the invention as defined by the appended claims.

110‧‧‧Cathode collector

120‧‧‧Cathodic active materials

130‧‧‧ separator

140‧‧‧Anode active material

150‧‧‧Anode collector

160‧‧‧Insulation

122‧‧‧ cathode

142‧‧‧Anode

T1‧‧‧ total length

T2‧‧‧ exposed part

T3‧‧‧ non-overlapping areas

Claims (14)

An electrode group comprising: a cathode and an anode, wherein a cathode collector and an anode collector are respectively coated with a cathode active material and an anode active material; and a separator interposed between the cathode and the anode, wherein an insulating layer is located Formed on the tab components of the cathode collector of the cathode. The electrode assembly of claim 1, wherein the insulating layer is between the cathode collector and the separator, and a portion of the insulating layer is placed to overlap with a region coated with the anode active material. The electrode group of claim 2, wherein the insulating layer is attached to an end of a region coated with the cathode active material. The electrode assembly of claim 3, wherein the insulating layer has an exposed portion, and one end of the tab member is exposed at the exposed portion. The electrode assembly of claim 4, wherein the insulating layer has a width of from about 1 mm to about 20 mm. The electrode assembly of claim 5, wherein the insulating layer has a thickness of from about 1 micron to about 100 microns. The electrode assembly of claim 1, wherein the insulating layer is obtained by applying an insulating material containing at least one ceramic material. The electrode group of claim 7, wherein the insulating layer is formed of at least one material selected from the group consisting of titanium dioxide, calcium carbonate, and barium sulfate or a mixture of at least two materials. The electrode group of claim 8, wherein the insulating layer is at least one material selected from the group consisting of titanium dioxide, calcium carbonate, and barium sulfate by applying from about 10% by weight to about 90% by weight. Or a solution or lacquer of a mixture of at least two materials, and then drying the coating. The electrode group of claim 1, wherein the insulating layer is obtained by bonding and applying a polymer film or emulsion having a weight average molecular weight of about 200,000 or less to the tab member. The electrode group of claim 10, wherein the polymer film is selected from the group consisting of polyacrylate, polystyrene, polyacrylic acid, polyacrylonitrile, polyethylene, polypropylene, polyimine, polyamine. Formed from at least one material of the group consisting of esters, polyethylene terephthalate, and combinations thereof. The electrode assembly of claim 1, wherein the insulating layer comprises a styrene-butadiene rubber (SBR) based polymer. An electrochemical device comprising at least one of the electrode groups of any one of claims 1 to 12. The electrochemical device of claim 13, wherein the electrochemical device is selected from the group consisting of a secondary battery, a battery module including a plurality of secondary batteries, and a battery pack including a plurality of battery modules. one.