KR100804411B1 - Electrode Assembly of Novel Structure and Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention is an electrode assembly having a separator interposed between the positive electrode and the negative electrode, the positive electrode and / or the electrode assembly comprising a structure in which the electrode active material is applied to the surface of the current collector of the circular or polygonal shape on a horizontal cross-section and its It provides a secondary battery consisting of.

Electrode assembly according to the present invention has a structure that is completely different from the conventional electrode, it is easy to deform the electrode structure, has the advantages of excellent mechanical strength, small potential difference between electrodes, etc., if such an electrode assembly is used, various structures And it can manufacture a secondary battery having an application field.

Description

Electrode Assembly of Novel Structure and Secondary Battery Comprising the Same

1 is a schematic diagram of an electrode assembly formed by integrating a plurality of positive and negative electrodes each having an active material coated on a surface of a current collector that is circular on a horizontal cross section according to one embodiment of the present invention;

FIG. 2 is a schematic diagram of an electrode assembly formed by integrating a plurality of positive and negative electrodes each having active materials coated on a surface of a rectangular current collector on a horizontal cross section according to another embodiment of the present invention; FIG.

FIG. 3 is a schematic diagram of an electrode assembly interposed between a positive electrode and a negative electrode in which a single sheet-type separator is integrated in a line in accordance with one embodiment of the present invention; FIG.

4 is a schematic diagram of an electrode assembly in which a composite sheet-type separator forms an independent partition and is separated by unit electrodes according to another embodiment of the present invention;

FIG. 5 is a schematic view of a battery in which a plurality of small linear electrodes (anode and cathode) are mounted in a compact state in a cylindrical battery case and form an overall long cylindrical structure according to one embodiment of the present invention; FIG.

FIG. 6 is a schematic view of a battery in which a plurality of short electrodes in a longitudinal direction of a horizontal cross section are stacked in a width direction according to another embodiment of the present invention and mounted in a box type battery case.

The present invention relates to a secondary battery having a novel structure, and more particularly, the positive electrode and / or the negative electrode has a structure in which the active material is coated on the surface of the current collector of the circular or polygonal shape on a horizontal cross-section, Compared to the electrode of the plate-like structure, the deformation in the longitudinal direction is easy to manufacture a battery having a variety of structures, and to a secondary battery having a number of advantages, such as to minimize the potential difference between the electrodes.

Recent developments in wireless communication technology have led to the popularization of mobile devices, and also tends to wirelessize many kinds of conventional devices. In this wireless technology, a secondary battery is essentially used as a power source of a device. In addition, electric vehicles, hybrid battery vehicles, and the like are being developed in terms of prevention of environmental pollution, such a driving device also needs a secondary battery as a power source. As described above, the usage of secondary batteries is rapidly increasing in many fields, and their outputs and capacities as well as shapes thereof are diversified according to the characteristics of the fields used.

In general, a secondary battery is formed by applying an active material to the surface of a plate-shaped current collector to form a positive electrode and a negative electrode and interposing a separator therebetween to form an electrode assembly, and then a pouch-shaped case of a cylindrical or rectangular metal can or an aluminum laminate sheet. Mounted therein, the electrode assembly is prepared by mainly injecting or incorporating a liquid electrolyte or by using a solid electrolyte.

Such an electrode assembly has a form of a jelly-roll wound around a long plate-shaped anode and a cathode or a plurality of unit electrodes sequentially stacked to provide a large capacity. Thus, the structure of the electrodes (anode and cathode) in the electrode assembly is essentially plate-shaped.

The plate-shaped electrode structure has the advantage of being able to be wound or laminated with high integration, but has a limitation in that deformation is difficult as necessary in the state of being made in the form of an electrode assembly. In addition, there are a number of problems, such as sensitive to the volume change of the electrode during charge and discharge, the generated gas is not easily discharged, the potential difference between the electrodes can be large.

In particular, despite the diversification of the types of devices in which secondary batteries are used, it is essential to require a separate part or space in which such a secondary battery of cylindrical, square or pouch type can be mounted. It is a big obstacle in terms of expansion. For example, when a new device has been developed and the space where the secondary battery can be mounted in such a device is narrow and long, the secondary battery including the electrode assembly based on the plate-shaped electrode is structurally changed as it is now. It is inherently impossible or very inefficient.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

That is, an object of the present invention is to provide an electrode assembly having a new structure, which has a structure different from that of a conventional electrode, which is easy to deform the electrode structure, and has the advantages of excellent mechanical strength and small potential difference between electrodes. .

Still another object of the present invention is to provide a secondary battery that can be manufactured in various forms by including the electrode assembly as described above.

The electrode assembly according to the present invention for achieving this object is an electrode assembly having a separator interposed between the positive electrode and the negative electrode, the positive electrode and / or the negative electrode on the horizontal cross-section of the current collector of the circular or polygonal shape of the electrode active material It is characterized by consisting of a structure that is applied.

That is, unlike conventional electrode assemblies having a structure in which an electrode active material is applied to a two-dimensional current collector surface such as a metal foil, the electrode assembly of the present invention has a horizontal cross-section, such as a three-dimensional current collector surface such as a circular or polygonal shape. This is fundamentally different in that the electrode active material is coated on the.

The contents of the present invention will be described in detail below.

In the present specification, the circular structure is a concept including an asymmetric elliptical structure in addition to a geometrically symmetrical circular shape. The polygonal structure is not particularly limited as long as it is not a two-dimensional plate-shaped structure, and examples thereof include a triangle, a square, a pentagon, a hexagonal structure, and the like, and each corner thereof has an angular shape and a round shape. Included.

The electrode active material is applied to the surface of the current collector having a circular or polygonal structure, and functions to move electrons through the current collector by occluding and releasing ions from the electrolyte to the electrolyte as in the conventional secondary battery.

This particular electrode structure may be applied to the positive electrode and / or the negative electrode, and preferably, the electrode assembly may be configured with both the positive electrode and the negative electrode having the three-dimensional structure as described above. For example, a schematic diagram illustrating an electrode assembly by integrating a plurality of positive and negative electrodes each having active materials coated on a surface of a current collector that is circular on a horizontal cross section is shown in FIG. 1. In addition, FIG. 2 is a schematic diagram of an electrode assembly in which the shape of the current collectors of the positive electrode and the negative electrode is rectangular in a horizontal section in the integrated structure as shown in FIG. 1.

In the electrode assembly according to the present invention, the separator which serves to electrically insulate the positive electrode and the negative electrode may be included in various forms. For example, the structure which the separator is apply | coated to the outer surface of the active material of a positive electrode and / or a negative electrode is mentioned. In this case, when the active material is coated with a uniform thickness on the surface of the current collector, the separator is also applied to the outer surface in the horizontal cross-sectional shape of the current collector. In this regard, the electrode assembly of FIGS. 1 and 2 has a structure in which a separator is coated with a uniform thickness on the outer surface of the anode.

As another example, the separator may be formed in a sheet form and interposed between the positive electrode and the negative electrode without being coated on the outer surface of the positive electrode or the negative electrode. Such a sheet may be in the form of a single sheet integrating electrodes of the same polarity in the form of a line or a cluster and interposed between them and electrodes of different polarity, or forming a plurality of independent compartments, one or the same in each of the compartments. It may be in the form of a composite sheet in which two or more electrodes of polarity are inserted. In this regard, FIG. 3 illustrates a structure of an electrode assembly interposed between a positive electrode and a negative electrode in which a single sheet-type separator is integrated in a line. In the electrode assembly of FIG. 1, the separator is coated on the outer surface of the active material of the positive electrode. However, in the electrode assembly of FIG. 3, the separator is not separately coated on the outer surface of the positive electrode due to the single sheet separator.

In addition, FIG. 4 illustrates a structure of an electrode assembly in which a composite sheet-type separator forms an independent partition and is separated by unit electrodes. The separator forming the independent compartments may be prepared by thermally fusion bonding a plurality of single sheets or by modifying the shape of the nozzle when extruding the resin for the separator.

The integration form of the electrodes in the electrode assembly of the present invention may vary according to the form in which a plurality of positive and negative electrodes are arranged, and in particular, an appropriate structure may be determined according to the horizontal cross-sectional shape of the current collector. For example, the structure in which the anode and the cathode are alternately arranged in one direction on the horizontal cross section, the structure in which the anode and the cathode are alternately arranged in the vertical both directions on the horizontal cross section may be possible.

1 shows a structure in which the anode and the cathode of the circular cross-sectional shape are alternately arranged only in one direction (X axis). On the other hand, Figure 2 shows a structure in which the anode and the cathode of the square cross-sectional shape are alternately arranged in both directions (X axis and Y axis), respectively.

The sizes and shapes of the respective electrodes constituting the electrode assembly are not necessarily the same. For example, in the case of an electrode having a circular cross-sectional structure, some electrodes having a small aperture may be disposed between the electrodes having a large aperture so as to provide a high density.

The present invention also provides a secondary battery comprising the electrode assembly as described above. The structure of the secondary battery according to the present invention is not particularly limited as long as the structure includes the electrode assembly as described above.

For example, it may be a structure in which a plurality of positive and negative electrodes extending in a vertical direction, that is, a lengthwise direction with respect to a horizontal cross section is mounted in a corresponding battery case, and an exemplary structure thereof is shown in FIG. 5. It is. That is, in the battery of FIG. 5, a plurality of small linear electrodes (anode and cathode) are mounted in a compact state in a cylindrical battery case, thereby forming a long cylindrical structure as a whole. The battery of this structure can be flexibly flexed as a whole since the constituent electrodes each take the form of an element wire, which can be useful even when the mounting space in the device is very limited. Such a battery may be manufactured in a structure in which a plurality of the small linear electrodes are twisted in a string form and mounted in a cylindrical battery case, or a plurality of unit cells in which the small linear electrodes are mounted in a cylindrical case are twisted in a string form. May be

As another example, a structure in which a plurality of short electrodes in the longitudinal direction of the horizontal cross section may be widely stacked in the width direction and mounted in a corresponding battery case, and an exemplary structure thereof is illustrated in FIG. 6. Referring to FIG. 6, a plurality of elliptical electrodes (anode and cathode) are mounted in a densely packed box-shaped battery case, and a cover is coupled to both end surfaces thereof to manufacture a battery. The outer surface of the cover is formed with external input / output terminals, respectively, and a connection circuit is formed on the inner surface that contacts the electrodes, and the connection terminals protrude at positions corresponding to the electrodes. For example, a circuit for connecting the cathodes in parallel is formed on the bottom cover, and the connection terminals protrude to contact the cathode portion of the electrode assembly.

As such, the secondary battery of the present invention may be manufactured in various forms, and in addition to the exemplary structure described above, various structures may be possible. For example, a sheet-shaped battery may be manufactured as a whole by arranging the electrodes in the form of wires as in FIG. 5 in a flat manner. Furthermore, the secondary battery according to the present invention can minimize the potential difference between the electrodes because the unit electrodes are smaller than the plate-shaped electrodes, and effectively reduce the expansion and contraction of the electrode generated during charging and discharging, considering the contact space between the unit electrodes Can be.

The secondary battery may be composed of various types, and among them, may be composed of a lithium secondary battery that can provide a high energy density and output.

In general, a lithium secondary battery is composed of an electrode assembly of a positive electrode, a negative electrode and a separator and a lithium salt-containing nonaqueous electrolyte.

The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder onto a positive electrode current collector, followed by drying, and optionally, a filler may be further added to the mixture.

The positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; 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 and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The material of the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode is manufactured by applying and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The material of the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver and the like on the surface, aluminum-cadmium alloy and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; 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, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; 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 metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separator is interposed between the anode and the cathode, and is an insulating thin film having high ion permeability and mechanical strength. The pore diameter is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium salt-containing non-aqueous electrolyte consists of a nonaqueous electrolyte and lithium. As the nonaqueous electrolyte, a nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, aceto Nitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used.

Examples of the organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyedgetion lysine, polyester sulfides, polyvinyl alcohols, polyvinylidene fluorides, Polymers containing ionic dissociating groups and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a good material to be dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, etc. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, in order to impart nonflammability, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

As described above, the electrode assembly according to the present invention has a completely different structure compared to the conventional electrode, and thus, the electrode structure is easily deformed, and has advantages such as excellent mechanical strength and small potential difference between electrodes.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (15)

An electrode assembly having a separator interposed between a positive electrode and a negative electrode, wherein the positive electrode and / or the negative electrode has a structure in which an electrode active material is coated on a surface of a current collector in a circular or polygonal shape on a horizontal cross section. The electrode assembly according to claim 1, wherein the circular structure is a geometrically perfect symmetrical circular and asymmetrical elliptical structure, and the polygonal structure is a triangular, square, pentagonal or hexagonal structure. The electrode assembly of claim 1, wherein a separator is coated on an outer surface of the active material of the positive electrode and / or the negative electrode. The electrode assembly according to claim 1, wherein the separator is interposed between the positive electrode and the negative electrode in a sheet form without being applied to the outer surface of the positive electrode or the negative electrode. The electrode assembly according to claim 4, wherein the separator is in the form of a single sheet interposed between electrodes of the same polarity and electrodes of the opposite polarity integrated in the form of a row or a cluster. The electrode assembly according to claim 4, wherein the separator forms a plurality of independent compartments in which two or more electrodes of one or the same polarity are inserted into each compartment. The electrode assembly according to claim 1, wherein the anode and the cathode are alternately arranged in one direction on a horizontal cross section. The electrode assembly according to claim 1, wherein an anode and a cathode are alternately arranged in both directions on a horizontal cross section. A secondary battery comprising the electrode assembly according to any one of claims 1 to 8. The secondary battery of claim 9, wherein an electrode assembly of a plurality of positive and negative electrodes extending in a longitudinal direction with respect to a horizontal cross section is mounted in a battery case. The secondary battery of claim 10, wherein the battery case has a cylindrical shape or a sheet shape. The secondary battery according to claim 10, wherein an electrode assembly including a plurality of small linear electrodes (anode and cathode) is mounted in a compact form in a cylindrical battery case. The secondary battery of claim 12, wherein the secondary battery is manufactured by twisting a plurality of the small linear electrodes in a string form, or by twisting a plurality of the unit cells in which the plurality of small linear electrodes are mounted in a cylindrical case. . The secondary battery of claim 9, wherein a plurality of electrodes short in the horizontal direction of the horizontal cross section are stacked in the width direction and mounted in the battery case. The secondary battery of claim 9, wherein the battery is a lithium secondary battery.

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