KR101634772B1 - Battery Cell Comprising Zigzag Type Electrode Assembly - Google Patents

Abstract

The present invention relates to a battery cell in which an electrode assembly having a first separator interposed between a chargeable and dischargeable positive electrode and a negative electrode is embedded in a battery case, wherein the battery case has a relatively large thickness- A hexahedral structure; Each electrode is coated with an electrode active material layer on one surface or both surfaces of a sheet-like current collector facing the opposite electrode; A laminated sheet having a structure in which a first separating film is interposed between a positive electrode sheet and a negative electrode sheet is embedded in a battery case with a structure bent in a zigzag shape corresponding to the inner surface shape of the battery case .

Description

[0001] The present invention relates to a battery cell including a zigzag electrode assembly,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery cell including a zigzag electrode assembly, and more particularly to a battery cell having an electrode assembly in which a first separator is interposed between a chargeable and dischargeable positive electrode and a negative electrode, Wherein the battery case has a hexahedron structure having a relatively large width to thickness ratio with respect to the position of the electrode terminal; Each electrode is coated with an electrode active material layer on one surface or both surfaces of a sheet-like current collector facing the opposite electrode; A laminated sheet having a structure in which a first separating film is interposed between a positive electrode sheet and a negative electrode sheet is embedded in a battery case with a structure bent in a zigzag shape corresponding to the inner surface shape of the battery case .

The secondary battery, which has recently been used in an increasing amount, has a high demand for a prismatic secondary battery and a pouch-type secondary battery that can be applied to products such as mobile phones with a thin thickness in terms of the shape of the battery. , Lithium secondary batteries, lithium ion batteries, and the like, which have advantages such as high output stability and output stability.

The secondary battery may be classified according to how the electrode assembly having the anode / separator / cathode structure is formed. Typically, the jelly-roll having the structure in which the anode and the cathode are wrapped with the separator interposed therebetween, (Wound type) electrode assembly, a stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a predetermined size unit are sequentially stacked with a separator interposed therebetween.

However, such conventional electrode assemblies have some problems.

First, since the jelly-roll electrode assembly is formed into a cylindrical or elliptical structure by winding a long sheet-like anode and cathode in a densified state, the stress caused by the expansion and contraction of the electrode during charging and discharging is accumulated in the electrode assembly When such a stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. As a result of the deformation of the electrode assembly, the spacing between the electrodes becomes uneven, resulting in a sudden drop in the performance of the battery and a risk of the safety of the battery being damaged due to an internal short circuit. Further, when the amount of loading of the active material per unit area of the anode is large or when the sheet-like positive electrode and negative electrode are wound by the characteristic of the material, cracks may be generated or broken in the folded portion, The negative electrode and the negative electrode must be wound. Therefore, it is difficult to rapidly wind the positive electrode and the negative electrode while keeping the distance between the positive electrode and the negative electrode constant, and thus the productivity is lowered.

Secondly, since the stacked electrode assembly requires a plurality of anode and cathode unit members to be sequentially stacked, a preparation process of the electrode plate for manufacturing the unit member is separately required, and the sequential stacking process requires a lot of time and effort, There is a problem.

In order to solve these problems, an electrode assembly of advanced structure which is a mixed type of the jelly-roll type and the stack type is used. The electrode assembly includes a bi-cell or a pull cell A stack / folding type electrode assembly having a structure in which full cells are wound by using a long continuous film is developed and disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059, 2001 -0082060.

Figures 1 and 2 schematically illustrate an exemplary structure and fabrication of such a stack / foldable electrode assembly.

Referring to these drawings, a plurality of pull cells 10, 11, 12, 13, 14, ... each having a positive electrode / separator / negative electrode laminated sequentially as unit cells are superimposed, Respectively. The separating film 20 has a unit length that can wrap around the pull cell and is bent inward for each unit length and starts from the center pull cell 10 and continues from the outermost pull cell 14 to each of the pull cells, Respectively. The distal end of the separation film 20 is thermally fused or bonded with an adhesive tape 25 or the like.

This stack / folding type electrode assembly is formed by arranging the pull cells 10, 11, 12, 13, 14 ... on the long length of the separation film 20 and separating the separation films 20 at one end 21 ) And then winding them sequentially.

The first pull cell 10 and the second pull cell 11 are located at a distance separated by a width corresponding to at least one pull cell, The lower surface electrode of the first pull cell 10 is brought into contact with the upper surface electrode of the second pull cell 11 after the outer surface of the first pull cell 10 is completely coated with the separation film 20.

Since the application length of the separation film 20 is increased in sequential laminating processes by winding the pull cells 11, 12, 13, 14, etc. after the second pull cell, the intervals between them in the winding direction are sequentially increased Respectively.

The first pull cell 10 and the second pull cell 11 are formed such that the upper surface electrode is a pull cell and the third pull cell 12 is a cathode. Is a pull cell in which a top surface electrode is a negative electrode, a fourth pull cell 13 is a pull cell in which an upper surface electrode is an anode, and a fifth pull cell 14 is a pull cell in which a top surface electrode is a cathode. That is, except for the first pull cell 10, the upper surface electrode is a sequential arrangement in which the pull cell, which is an anode, and the pull cell, which is a cathode, are alternated. On the other hand, although not shown, when a unit cell is a bicycle, the bicells are mounted in an array alternating in two units.

Therefore, the stack / folding type electrode assembly significantly complements the disadvantages of the jelly-roll and the stacked electrode assembly. However, in order to laminate the separating film so as to be opposite electrodes at the contact interface between the unit cells, There is a problem that the manufacturing process becomes complicated and the productivity is lowered because the full cells must be sorted by type and mounted with predetermined rules. Furthermore, since it is very difficult to distinguish unit cells by type, when any one of the unit cells is missing or misaligned due to various causes such as negligence in operation or errors in the process of mounting on a separation film, There is a possibility that the performance of the battery may deteriorate.

However, since the above problems exist in terms of productivity, it is possible to improve productivity and operation performance by compensating for the above disadvantages. There is an increasing need for an electrode assembly that can provide such an electrode assembly.

Particularly, a large-sized battery module used in middle and large-sized devices such as electric vehicles and hybrid electric vehicles, which have attracted much attention in recent years, requires a large number of battery cells (unit cells) and long life characteristics , There is an urgent need for a technique for an electrode assembly having a novel structure capable of solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

That is, an object of the present invention is to provide an electrode assembly in which a laminated sheet having a structure in which a first separator is interposed between a positive electrode sheet and a negative electrode sheet is bent in a zigzag shape corresponding to the inner surface shape of the battery case, In order to solve the safety problem of the conventional jelly-roll or stack / folding type electrode assembly, there is no restriction on the process variation according to the number of bicells compared with the stack / folding process, A battery cell in which an electrode assembly capable of securing life and stability is built in a battery case.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a battery cell including an electrode assembly having a first separator interposed between a chargeable and dischargeable anode and a cathode,

Wherein the battery case has a hexahedron structure having a relatively large width in thickness with respect to a position of an electrode terminal;

Each electrode is coated with an electrode active material layer on one surface or both surfaces of a sheet-like current collector facing the opposite electrode;

A laminated sheet having a structure in which a first separator is interposed between a positive electrode sheet and a negative electrode sheet is structured to be embedded in a battery case with a structure bent in a staggered shape corresponding to the inner surface shape of the battery case.

That is, according to the present invention, in the laminated sheet having the structure in which the first separating film is interposed between the positive electrode sheet and the negative electrode sheet, the electrode assembly is formed by folding in a zigzag shape corresponding to the inner surface shape of the battery case, There is no restriction of the process variation according to the number of bicells compared with the folding process and it can be easily manufactured through simplification of the process and the life of the battery and the life time of the cell are improved so as to solve the safety problem of the existing jelly- It is possible to provide an electrode assembly capable of securing stability.

Such a structure not only solves the problems of cracking and rupture caused by the winding structure of the jelly-roll, but also has no restriction on the process variation according to the number of bicells compared with the stack / folding process, And it is possible to solve the safety problem of the conventional stack / folding type electrode assembly, thereby securing the life and stability of the battery.

In one specific example, the width of the battery case may be 1.5 to 50 times the thickness of the battery case, and the positive electrode sheet and the negative electrode sheet may be bonded to the first separating film.

In addition, the total amount of the active material of the positive electrode is smaller than the total amount of the active material of the negative electrode. Specifically, the total amount of the active material of the positive electrode may be 80 to 99% based on the total amount of the active material of the negative electrode.

In another specific example, the electrode assembly may have a structure in which a second separation membrane is attached to the outer surface of the cathode sheet, and a third separation membrane is attached to the outer surface of the cathode sheet.

The electrode assembly may be configured such that the positive electrode and the negative electrode are folded in a zigzag manner so that the positive electrode and the negative electrode are facing each other, and the second separator or the third separator extends around the outer periphery of the electrode assembly to surround the electrode assembly.

The battery case may be, for example, a square metal can. The prismatic secondary battery includes a positive electrode sheet and a negative electrode sheet in a state in which a separation membrane is interposed therebetween and a jelly-roll having a protective tape attached thereto to wrap the outer surface thereof. , Inserting it into a square can, impregnating the electrolyte, and sealing the can.

In addition, the secondary battery according to the present invention can be suitably applied to a pouch-type secondary battery in which an electrode assembly is embedded in a storage portion of a pouch-type case of a laminate sheet including a metal layer and a resin layer, for example, an aluminum laminate sheet have.

The battery according to the present invention is preferably a lithium ion secondary battery in which a lithium-containing electrolyte is impregnated in an electrode assembly, a lithium secondary battery such as a so-called lithium ion polymer battery in which an electrode assembly is impregnated with a lithium- Can be applied.

Generally, a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte containing a lithium salt.

The positive electrode is prepared, for example, by coating a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the mixture. Optionally, a filler may be further added to the mixture.

The cathode 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 and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where 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} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like. However, the present invention is not limited to these.

The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey 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 which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, 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 suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin 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 active material on a negative electrode collector, and if necessary, the above-described components may be selectively included.

Examples of the negative electrode active material include carbon such as non-graphitized carbon and 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 < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{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; Li-Co-Ni-based materials and the like can be used.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m, and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The non-aqueous electrolyte solution containing a lithium salt is composed of a polar organic electrolyte and a lithium salt. As the electrolytic solution, a non-aqueous liquid electrolytic solution, an organic solid electrolyte, an inorganic solid electrolyte and the like are used.

Examples of the nonaqueous liquid electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation 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 and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble 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.

For the purpose of improving the charge-discharge characteristics and the flame retardancy, the non-aqueous liquid electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride and the like are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The present invention can also provide a device including the battery cell as a unit cell.

The device according to the present invention can be preferably used for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device, as well as a mobile device such as a mobile phone and a portable computer, as well as excellent lifetime characteristics and safety.

As described above, the battery cell according to the present invention has a structure in which a laminated sheet having a structure in which a first separator is interposed between a positive electrode sheet and a negative electrode sheet is bent in a zigzag shape corresponding to the inner surface shape of the battery case By forming the electrode assembly, there is no restriction of the process variation according to the number of bicells compared with the stack / folding process, and it can be easily manufactured by simplifying the process, and the safety problem of the conventional jelly-roll or stack / folding type electrode assembly It is possible to provide a battery cell in which an electrode assembly capable of ensuring the life and stability of the battery is built in the battery case.

1 is a schematic diagram of an exemplary structure of a conventional stack / folding type electrode assembly;
FIG. 2 is a schematic diagram illustrating an exemplary arrangement of unit cells in a manufacturing process of the stack / folding type electrode assembly of FIG. 1; FIG.
3 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention;
4 is a cross-sectional view of an electrode assembly according to another embodiment of the present invention;
5 is a schematic view of an electrode assembly according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

3 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention.

3, the battery cell according to the present invention includes an electrode assembly 100 having a first separator 130 interposed between a chargeable and dischargeable anode 110 and a cathode 120, The positive electrode 110 and the negative electrode 120 are coated with an electrode active material layer on both sides of a sheet-like current collector facing the opposite electrode, and the positive electrode sheet 110 and the negative electrode sheet 120 The electrode assembly 100 having the first separator 130 interposed therebetween is embedded in the battery case in a structure in which the electrode assembly 100 is folded in a zigzag shape.

The positive electrode sheet 110 and the negative electrode sheet 120 are bonded to each other with the first separator 130. The total amount of the active material of the positive electrode is smaller than the total amount of the active material of the negative electrode. And 90% as a reference.

FIG. 4 is a cross-sectional view of an electrode assembly according to another embodiment of the present invention, and FIG. 5 is a schematic view of an electrode assembly according to another embodiment of the present invention.

Referring to these drawings, an electrode assembly 200 according to another embodiment of the present invention includes an electrode assembly 210 having a structure in which a first separator 230 is interposed between a positive electrode sheet 210 and a negative electrode sheet 220 The second separator 240 is attached to the outer surface of the anode sheet 210 and the third separator 250 is formed on the outer surface of the anode sheet 220 The electrode assembly 100 of FIG. 1 differs from the electrode assembly 100 of FIG.

The electrode assembly 200 includes a second separator 240 attached to the outer surface of the cathode sheet 210 and extending from the electrode assembly 200 using an extended portion 241 extending in a manner to surround the outer surface of the electrode assembly 200. [ As shown in FIG.

In the electrode assembly shown in FIGS. 4 and 5, the second separator has an extended portion extending in the form of wrapping the outer surface of the electrode assembly. However, in the first separator and the third separator, The electrode assembly may be formed to have a structure that surrounds the outer surface of the electrode assembly through an extended portion extending from the electrode assembly.

As shown in Figs. 3 to 5, according to the present invention, in a laminated sheet having a structure in which a first separator is interposed between a positive electrode sheet and a negative electrode sheet, a structure that is bent in a staggered shape corresponding to the inner surface shape of the battery case It is possible to easily manufacture the electrode assembly by simplifying the process without the restriction of the process variation according to the number of bicells compared with the stack / folding process, and the safety of the conventional jelly-roll or stack / folding type electrode assembly It is possible to provide a battery cell in which an electrode assembly capable of ensuring the life and stability of the battery is provided in the battery case so as to solve the problem.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (14)

A battery cell in which an electrode assembly having a first separator interposed between a positive electrode and a negative electrode capable of charge and discharge is built in a battery case,
Wherein the battery case has a hexahedron structure having a relatively large width in thickness with respect to a position of an electrode terminal;
Each electrode is coated with an electrode active material layer on one surface or both surfaces of a sheet-like current collector facing the opposite electrode;
The laminated sheet having a structure in which the first separator film is interposed between the positive electrode sheet and the negative electrode sheet is built in the battery case with a structure bent in a zigzag shape corresponding to the inner surface shape of the battery case,
A second separation membrane is attached to the outer surface of the cathode sheet, a third separation membrane is attached to the outer surface of the cathode sheet,
The second separator or the third separator may extend in a manner to surround the outer circumferential surface of the electrode assembly,
Wherein the positive electrode sheet and the negative electrode sheet are adhered to each other with the first separating membrane. The battery cell according to claim 1, wherein the width of the battery case is 1.5 to 50 times the thickness of the battery case. The battery cell according to claim 1, wherein the battery case is a square metal can. The battery cell according to claim 1, wherein the battery case is a pouch-shaped case made of a laminate sheet including a metal layer and a resin layer. The battery cell according to claim 4, wherein the laminate sheet is an aluminum laminate sheet in which the metal layer is aluminum or an aluminum alloy. delete The battery cell according to claim 1, wherein the total amount of active material in the positive electrode is smaller than the total amount of active material in the negative electrode. The battery cell according to claim 7, wherein the total amount of the active material of the positive electrode is 80 to 99% based on the total amount of the negative electrode active material. delete delete The battery cell according to claim 1, wherein the anode comprises a lithium transition metal oxide as an electrode active material. 2. The battery according to claim 1, wherein the negative electrode comprises at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a tin-based active material, a silicon-tin oxide, and a silicon- Cell. A device comprising a battery cell according to any one of claims 1 to 5, 7, 8, 11 and 12 as a unit cell. 14. The device of claim 13, wherein the device is selected from a cell phone, a tablet computer, a notebook computer, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

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