KR101606442B1 - Battery Cell Comprising Unit Cells Having Different Electrode Structures - Google Patents

Abstract

The present invention relates to an electrode comprising a positive electrode and a negative electrode coated with an active material on both sides of a current collector, unit cells having a laminated structure composed of a separator interposed between the positive and negative electrodes, and a separation film for continuously winding up the unit cells. The assembly being mounted on a receiving portion of the battery case; Wherein the innermost unit cell and the outermost unit cell of the electrode assembly have a laminated structure in which electrodes of different polarities are independently located at both ends of the unit cell; Wherein the unit cells except for the innermost unit cell and the outermost unit cell have a laminated structure in which electrodes of the same polarity are independently positioned at both ends of the unit cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell having a plurality of unit cells,

The present invention relates to a battery cell in which the electrode structure includes different unit cells.

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, as technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

The secondary battery includes a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch type battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet .

In particular, in recent years, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet has attracted much attention due to low manufacturing cost, small weight, And its usage is gradually increasing.

Also, the secondary battery is classified according to the structure of the electrode assembly having the positive electrode, the negative electrode, and the separator interposed between the positive electrode and the negative electrode. Typically, the long battery- 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, the jelly-roll type (wound type) electrode assembly having a structure in which a separator is interposed; In recent years, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, an electrode assembly having an advanced structure, which is a combination of the jelly-roll type and the stack type, A stack / folding type electrode having a structure in which unit cells stacked with a separator interposed between an anode and a cathode are sequentially wound while being placed on a separation film Developed body lip.

FIG. 1 schematically illustrates a typical structure of a conventional stack / folding type electrode assembly.

Referring to FIG. 1, the electrode assembly 100 includes unit cells 120, 140, 160, and 180 having a structure in which a cathode is disposed between anodes and a separation membrane is disposed between anodes and a cathode, And a unit cell 110, 130, 150, 170 having a structure in which a separator is interposed between the anode and the cathode.

The separation film 190 interposed between the unit cells 110, 120, 130, 140, 150, 160, 170 and 180 of the electrode assembly 100 is formed of a unit cell 120, 130, 140, 150, 160, 170, 180. The electrode assembly 100 includes a plurality of unit cells 110, 120, 130 , 140, 150, 160, 170, 180) and winding the separation film (190).

The anode 181 at the lowermost end of the electrode assembly 100 is configured such that the active material is applied to only one side of the current collector in the inward direction of the electrode assembly 100 and the other side of the cathode current collector faces the separation film 190 .

Therefore, the electrode assembly 100 includes a total of eleven positive electrodes 102, twelve negative electrodes 103, one positive electrode section 181, sixteen separation membranes 101, and one separation film 190.

However, in the case of such a stack / folding type electrode assembly, since the outermost electrodes of the unit cells have the same lamination structure, the unit cells of the lamination structure have a larger amount of cells Or an inactive material such as a separator. Accordingly, there is a problem in that the energy density proportional to the thickness of the battery cell is not satisfied, and there is a problem in that the overall capacity of the battery cell is limited.

Therefore, there is a high need for a technique capable of fundamentally solving such 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.

The inventors of the present application have conducted intensive research and various experiments, and have found that, as will be described later, the unit cells of the innermost unit cell and the outermost unit cells of the unit cells of the laminated structure in which the electrodes of different polarity are located at both ends It is possible to increase the application amount of the active material by the thickness of the separator and the current collector reduced compared to the conventional battery cell having only the unit cells of the laminated structure in which the electrodes of the same polarity are located at both ends, , It was confirmed that the overall capacity can be easily improved without changing the structure or shape of the battery cell, and the present invention has been accomplished.

According to an aspect of the present invention, there is provided a battery cell comprising:

An electrode assembly including a positive electrode and a negative electrode coated with an active material on both sides of a collector, a unit cell having a laminated structure composed of a separator interposed between the positive and negative electrodes, and a separator film for continuously winding the unit cells, And is mounted on a receiving portion of the case;

Wherein the innermost unit cell and the outermost unit cell of the electrode assembly have a laminated structure in which electrodes of different polarities are independently located at both ends of the unit cell;

The unit cells except for the innermost unit cell and the outermost unit cell have a laminated structure in which electrodes of the same polarity are independently located at both ends of the unit cell.

Therefore, the battery cell according to the present invention increases the application amount of the active material by the thickness of the reduced separator and the current collector, compared with the conventional battery cell having the unit cells of the laminated structure in which the electrodes of the same polarity are located at both ends, It is possible to exhibit a high capacity and to easily improve the overall capacity without changing the structure or the shape of the battery cell.

In one specific example, the unit cells except the innermost unit cell and the outermost unit cell of the electrode assembly have a stacked structure in which electrodes having the same polarity are located at both ends, and the unit cells and the cathodes, It may be a structure including all the unit cells located at both ends.

That is, the battery cell according to the present invention is a unit cell of an electrode assembly, in which a laminated structure in which electrodes of different polarities are located at both ends of a unit cell, a laminated structure in which an anode is located at both ends, It can be a structure that includes both.

However, the present invention is not limited thereto, and the electrode assembly may include a unit cell excluding the innermost unit cell and the outermost unit cell, wherein the unit cell includes only the unit cell in which the anode is located at both ends, It may be a structure including only a unit cell.

More specifically, when the electrode assembly includes four unit cells, the one innermost unit cell and the two outermost unit cells have a structure in which the polarities of the electrodes located at both ends are different from each other, , The polarity of the electrodes located at both ends may be the anode or the cathode may be the same depending on the stacking direction of the unit cells.

The number of unit cells of the electrode assembly may be an even number or an odd number. If the number of unit cells is an even number, the number of unit cells may be four or more, specifically eight, The polarities of the outer electrodes may be the same.

As described above, when the electrode assembly includes four unit cells, one innermost unit cell and two outermost unit cells have a laminated structure in which electrodes having different polarities are located at both ends of the unit cell, One unit cell except for the three unit cells has a stacked structure in which electrodes having the same polarity are located at both ends of the unit cell.

In this case, since the unit cell of the laminated structure in which the electrodes of the same polarity are located at both ends is located in the innermost unit cell of the laminated structure in which the electrodes of the different polarity are located at both ends, The unit cell located in the outermost unit cell forms an electrode having the same polarity as the other side of the innermost unit cell.

Therefore, when the number of unit cells of the electrode assembly is an even number, the outermost unit cell formed on one side and the other side of the innermost unit cell has a structure in which electrodes having the same polarity are located at the outermost portions of the battery cells. The outermost electrodes of the assembly may have a structure in which the polarities of the outermost electrodes are the same. Specifically, the polarities of the outermost electrodes may be composed of a cathode so as to suppress the generation of dendrite.

In another specific example, when the number of unit cells of the electrode assembly is an odd number, the number of electrode assemblies may be three or more, specifically, seven. In this case, the electrode assemblies may be structured such that the polarities of the outermost electrodes are different from each other. .

More specifically, when the electrode assembly includes five unit cells, one outermost unit cell of the electrode assembly including the four unit cells has a structure in which electrodes having the same polarity are located at both ends, A unit cell having a structure in which electrodes of different polarities are located at both ends is adjacent to a unit cell having a structure in which electrodes of the same polarity are located at both ends, is consequently positioned, so that the polarity of the outermost electrodes They can be made different from each other.

Meanwhile, in the electrode assembly, n unit cells are positioned on a separation film having a long length relative to the width, and the first unit cell is located at the innermost position and the n-1 th unit cell and the n th unit cell are located at the outermost position In order to prevent the deterioration of the film.

In other words, the electrode assembly is sequentially wound from the first unit cell to the n-th unit cell in a state where n unit cells are arranged on a long length of the separation film, so that the first unit cell is located at the innermost position, And the n-th unit cell and the n-th unit cell are located at the outermost positions, respectively, to form the outermost unit cells.

In this case, when the number n is an even number, a spacing corresponding to the size of the unit cell is formed between the first unit cell and the second unit cell on the separating film before winding, and the n- The unit cells may have a structure in which the electrodes of the same polarity are positioned so as to face the same direction.

Specifically, when the number n is an even number, the outermost electrodes of the electrode assembly are configured to have the same polarity, and after one of the n-1 unit cell and the n unit cell is wound, The electrodes of the same polarity are positioned on the separating film before winding so as to face in the same direction.

On the other hand, when n is an odd number, a separation region corresponding to the size of the unit cell is formed between the first unit cell and the second unit cell on the separation film before winding, and the n- It may be a structure in which electrodes of different polarity from the cell are positioned to face in the same direction.

Specifically, when the n is an odd number, the outermost electrodes of the electrode assembly are configured to have polarities different from each other, and after one of the n-1 unit cells and the n-th unit cells is wound, Are positioned on the outermost opposite sides, respectively, so that the electrodes having polarities different from each other on the separation film before winding are positioned so as to face in the same direction.

In the meantime, the unit cells may have the same thickness. In more detail, the electrode assembly may have a laminated structure in which electrodes having different polarities are disposed at both ends of the separator, The unit cells of the innermost unit cell and the unit cells of the outermost unit may be added to the unit cells of the laminated structure in which the electrodes of the same polarity are located at both ends, It may be a structure having the same thickness as the cell.

On the other hand, the unit cells of the laminated structure in which electrodes having the same polarity as the unit cells of the laminated structure in which the electrodes of different polarities are located at both ends are located at both ends, may be different in thickness.

Specifically, the active material to a degree corresponding to the thickness of the current collector and the separator reduced compared to the conventional battery cell is uniformly added to all the unit cells constituting the battery cell, so that the innermost unit cell and the outermost unit cell And may be a structure having a thickness different from that of a unit cell of a laminated structure in which electrodes of the same polarity are located at both ends.

In this case, the unit cells have a structure in which the amounts of the positive electrode active material or the negative electrode active material applied to one surface of the current collector are respectively the same. In the manufacturing process of the battery cell, the unit cells are divided into the innermost and outermost unit cells, The active material can be applied to one surface of the current collector, thereby reducing manpower and time required for the process.

In one specific example, the unit cells may have the same width and length, but the present invention is not limited thereto. In order to manufacture the unit cells in various forms according to the type and shape of the device on which the battery cells are mounted, Width and / or length may be different from each other.

The width indicates a distance between the outer circumferential surface adjacent to the outer circumferential surface where the electrode terminal of the unit cell protrudes and the length indicates the distance from the outer circumferential surface of the unit cell protruding to the opposite outer circumferential surface.

In one specific example, the battery cell according to the present invention is manufactured by attaching the electrode assembly of the above structure to the battery case, wherein the battery case includes a cylindrical or rectangular can, and a cap mounted on the open upper end of the can But is not limited thereto and may be a pouch type case of a laminate sheet including a resin layer and a metal layer.

Meanwhile, the battery cell according to the present invention is not particularly limited in its kind, but specific examples thereof include a lithium ion battery having advantages such as high energy density, discharge voltage, and output stability, a lithium secondary battery such as a lithium ion polymer battery, Lt; / RTI >

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.

Further, in one specific example, in order to improve the safety of a high energy density cell, the separation membrane and / or the separation film may be an organic / inorganic composite porous SRS (Safety-Reinforcing Separators) separator.

The SRS separator is manufactured by using inorganic particles and a binder polymer on the polyolefin-based separator substrate as an active layer component. In addition to the pore structure contained in the separator substrate itself, the SRS separator is formed by interstitial volume between inorganic particles And has a uniform pore structure.

The use of such an organic / inorganic composite porous separator has an advantage in that the increase in cell thickness due to swelling during formation can be suppressed as compared with the case where a conventional separator is used, When a gelable polymer is used when liquid electrolyte is impregnated, it can also be used as an electrolyte.

In addition, the organic / inorganic composite porous separator can exhibit excellent adhesion characteristics by controlling the contents of the inorganic particles and the binder polymer in the separator, so that the cell assembly process can be easily performed.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as the oxidation and / or reduction reaction does not occur in the operating voltage range of the applied battery (for example, 0 to 5 V based on Li / Li +). Particularly, when inorganic particles having an ion-transporting ability are used, the ion conductivity in the electrochemical device can be increased and the performance can be improved. Therefore, it is preferable that the ionic conductivity is as high as possible. In addition, when the inorganic particles have a high density, it is difficult to disperse the particles at the time of coating, and there is a problem of an increase in weight during the production of the battery. In the case of an inorganic substance having a high dielectric constant, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte also contributes to increase ionic conductivity of the electrolyte.

The nonaqueous 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 also provides a device comprising one or more of the battery cells, the device including at least one of a cell phone, a tablet computer, a notebook computer, a power tool, an electric vehicle, a hybrid electric vehicle, a plug- And a power storage device.

Such devices or devices are well known in the art, so a detailed description thereof will be omitted herein.

As described above, in the battery cell according to the present invention, the unit cell in the innermost unit cell and the unit cell in the outermost unit cell are formed of unit cells having stacked structure in which electrodes of different polarities are located at both ends, The amount of the active material applied is increased by the thickness of the separator and the current collector, which is smaller than that of the battery cell having only the unit cells of the stacked structure in which the electrode of the battery cell is located at both ends, The entire capacity can be easily improved by changing only the unit cell configuration of the innermost and outermost sides of the electrode assembly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing a general structure of a conventional stack / folding type electrode assembly; FIG.
2 is a schematic view illustrating a method of manufacturing an electrode assembly of a battery cell according to an embodiment of the present invention;
3 is a schematic view schematically showing a structure of a battery cell manufactured according to the manufacturing method of FIG. 2;
4 is a schematic view illustrating a method of manufacturing an electrode assembly of a battery cell according to another embodiment of the present invention;
5 is a schematic view schematically showing the structure of a battery cell manufactured according to the manufacturing method of FIG. 4;

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

FIG. 2 is a schematic view illustrating a method of manufacturing an electrode assembly of a battery cell according to an embodiment of the present invention.

Referring to FIG. 2, the electrode assembly 200 includes unit cells 212, 213, 214, 215, and 216 having electrodes of the same polarity positioned at both ends, and unit cells 211 , 217 and 218 are arranged on the separation film 220 in an alternating manner and the separation film 220 is wound.

Specifically, the electrode assembly 200 includes eight unit cells 211, 212, 213, 214, 215, 216, 217, and 218, and the first unit cell 211 and the seventh unit cell 217 and the eighth unit cell 218 have a stacked structure in which electrodes of different polarities are located at both ends and five unit cells 212 to 212 from the second unit cell 212 to the sixth unit cell 216, 213, 214, 215, and 216 have a laminated structure in which electrodes having the same polarity are located at both ends.

The second unit cell 212, the fifth unit cell 215, and the sixth unit cell 216 of the unit cells 211, 212, 213, 214, 215, 216, 217, And the third unit cell 213 and the fourth unit cell 214 are structured such that the anode is located at both ends.

The first unit cell 211 faces the separating film 220 toward the lower face of the anode 241 and extends from the second unit cell 212 to the eighth unit cell 211 along the electrode direction of the first unit cell 211. [ The unit cell 218 is located on the separation film.

The seventh unit cell 217 located at the outermost side of the electrode assembly 200 and the eighth unit cell 218 located at the outermost side of the electrode assembly 200 are disposed at the outermost portion of the electrode assembly 200, Are arranged such that the cathodes 242 and 243 face the separation film 220 toward the bottom, respectively.

The electrode assembly 200 is manufactured by winding the first unit cell 211 in the counterclockwise direction 250 from the first unit cell 211 to the eighth unit cell 218 so that the first unit cell 211 is positioned at the innermost position.

The first unit cell 211 and the second unit cell 212 are spaced apart from each other by a distance corresponding to the size of the unit cell, The separation film 220 is sandwiched between the cathode 244 located on the upper surface of the first unit cell 211 and the anode 245 located on the upper surface of the third unit cell 213. [

Specifically, the first unit cell 211 moves to the spaced-apart portion 230 between the first unit cell 211 and the second unit cell 212 in an inverted state during the winding process, The anode 241 located on the lower surface of the unit cell 211 is wound so as to face the anode 246 located on the upper surface of the second unit cell 212 and the separation film 220 therebetween.

The first unit cell 211 and the second unit cell 212 facing each other with the separation film 220 therebetween are simultaneously wound by the separation film 220 so that the first unit cell 211 A cathode 244 located on the upper surface of the third unit cell 213 faces the anode 245 located on the upper surface of the third unit cell 213 with the separation film 220 interposed therebetween.

The process progresses sequentially to the eighth unit cell 218, so that the first unit cell 211 is located on the innermost side and the seventh unit cell 217 and the eighth unit cell 217 218 are respectively disposed on the electrode assembly 200.

FIG. 3 is a schematic view schematically showing the structure of an electrode assembly manufactured according to the above manufacturing method.

Referring to FIG. 3 together with FIG. 2, the first unit cell 211, the seventh unit cell 217, and the eighth unit cell 218 of a laminated structure in which electrodes of different polarities are located at both ends, 200 and the outermost unit cells facing each other.

The electrode assembly 200 includes eight unit cells 211, 212, 213, 214, 215, 216, 217 and 218. The polarities of the outermost electrodes of the electrode assembly 200 are the same.

The first unit cell 211 of the electrode assembly 200 faces the upper surface of the cathode 244 so that the outermost electrodes are composed of the cathodes 242 and 243.

On the other hand, when the cathode 244 of the first unit cell 211 faces the bottom, the outermost electrodes of the electrode assembly 200 may be configured as an anode.

The electrode assembly 200 includes a total of 10 anodes, 11 cathodes, 13 separators and one separation film.

As a result, the number of separators as the inactive material is reduced and the number of the positive electrodes and the negative electrodes is reduced as compared with the conventional battery cells having only the unit cells of the laminated structure in which the electrodes of the same polarity are located at both ends, The total quantity of water is also reduced and the active material corresponding to the reduced thickness of the inert material can be added, so that the overall capacity of the battery cell increases.

In the electrode assembly 200, electrodes of the same polarity as the first unit cell 211, the seventh unit cell 217, and the eighth unit cell 218 of the laminated structure in which the electrodes of different polarities are located at both ends, The second unit cell 212 to the sixth unit cell 216 of the stacked structure are different in overall thickness from each other, and the amount of the active material reduced to the thickness of the collector and the separator Is uniformly added to all the unit cells 211, 212, 213, 214, 215, 216, 217, 218 constituting the battery cell.

Accordingly, since the coating amount of the active material on one side of the current collector of each of the unit cells 211, 212, 213, 214, 215, 216, 217, and 218 is uniform, The active material is uniformly applied to one surface of the current collector without distinguishing between the unit cell of the unit cell and the other unit cell, so that manpower and time required for the process can be reduced.

However, the present invention is not limited thereto, and the unit cells 211, 212, 213, 214, 215, 216, 217, and 218 of the electrode assembly 200 may have the same thickness, The first unit cell 211 having the laminated structure in which the electrodes having different polarities are located at both ends and the first unit cell 211 having the polarity opposite to that of the conventional battery cell and corresponding to the thickness of the separator, The first unit cell 211 and the seventh unit cell 217 at the outermost side and the seventh unit cell 217 at the outermost side can be additionally added to the unit cell 217 and the eighth unit cell 218, The cell 218 may have a structure having the same thickness as the second unit cell 212 to the sixth unit cell 216 of the stacked structure in which the electrodes of the same polarity are located at both ends.

4 is a schematic view illustrating a method of manufacturing an electrode assembly for a battery cell according to another embodiment of the present invention.

4, similarly to the electrode assembly 200 of FIG. 2, the electrode assembly 400 has electrodes of the same polarity different from those of the unit cells 412, 413, 414, and 415 located at both ends of the electrode assembly 400 By arranging the unit cells 411, 416, and 417 located at both ends in an alternating manner on the separation film 420 and winding the separation film 420 therebetween.

Specifically, the electrode assembly 400 includes seven unit cells 411, 412, 413, 414, 415, 416 and 417, and the first unit cell 411 and the sixth unit cell 416 And the seventh unit cell 417 are located at both ends of the fourth unit cell 415. Four unit cells 412, 413, and 413 from the second unit cell 412 to the fifth unit cell 415 are stacked, 414, and 415 have a laminated structure in which electrodes of the same polarity are located at both ends.

Unlike the electrode assembly of FIG. 2, the electrode assembly 400 includes an odd number of unit cells, and the anode and the cathode are located at the outermost portions of the electrode assembly 400. Accordingly, The anode 443 of the sixth unit cell 416 and the cathode 442 of the seventh unit cell 417 are arranged facing the separation film 420 toward the bottom.

The electrode assembly 400 is manufactured by winding the first unit cell 411 in the counterclockwise direction 450 from the first unit cell 411 to the seventh unit cell 417 so that the first unit cell 411 is located at the innermost position, The procedure is the same as in Fig.

FIG. 5 is a schematic view schematically showing the structure of the electrode assembly 400 manufactured according to the above manufacturing method.

Referring to FIG. 5, the first unit cell 411, the sixth unit cell 416, and the seventh unit cell 417 of a laminated structure in which electrodes of different polarities are located at both ends, 400 and the outermost unit cells facing each other.

The electrode assembly 400 includes seven unit cells 411, 412, 413, 414, 415, 416 and 417. The polarities of the outermost electrodes of the electrode assembly 400 are different from each other.

The first unit cell 411 of the electrode assembly 400 faces the upper surface of the first unit cell 411. The uppermost electrode of the first unit cell 411 is composed of the cathode 442, .

On the other hand, when the cathode 444 of the first unit cell 411 faces the bottom surface, the outermost electrodes of the electrode assembly 400 may be constituted by the anode at the uppermost end and by the cathode at the lowermost end.

The construction and effect of the other electrode assembly 400 are the same as those of the electrode assembly 200 of FIG.

The structure of the battery cell according to the present invention is not limited thereto and the battery cell may be manufactured by folding the unit cells in a structure in which the separation film is wrapped in a Z shape from the lowermost unit cell to the uppermost unit cell of the electrode assembly have.

Hereinafter, the present invention will be described with reference to Examples. However, the following Examples are intended to illustrate the present invention, and the scope of the present invention is not limited thereto.

≪ Example 1 >

The electrode assembly was assembled as shown in FIGS. 2 to 3, embedded in a pouch-shaped battery case, and impregnated with an EC / EMC electrolyte solution containing 1 M LiPF ₆ lithium salt to prepare a battery cell. At this time, the size of the battery cell was designed to be 3.5 mm * 79.6 mm * 92.5 mm.

≪ Comparative Example 1 &

The electrode assembly was assembled as shown in FIG. 1, embedded in a pouch-shaped battery case, and impregnated with an EC / EMC electrolyte solution containing 1 M LiPF ₆ lithium salt to prepare a battery cell. At this time, the size of the battery cell was designed to be 3.5 mm * 79.6 mm * 92.5 mm.

<Experimental Example 1>

The total loading amount of the positive electrode, the battery capacity, and the energy density were measured for the battery cells manufactured in Example 1 and Comparative Example 1, and the results are shown in Table 1 below.

division Number of Stack Anode loading
(mg / 25 cm2) Capacity (mAh) Energy density
(Wh / L) Example 1 8 503 3879 572 Comparative Example 1 433 3840 568

Referring to Table 1, the battery cell according to the present invention can increase the loading amount of the electrode active material as compared with a battery cell having only unit cells of a structure in which electrodes of the same polarity are located at both ends of the unit cell, And energy density increased by 1% and 0.7%, respectively.

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 (21)

An electrode assembly including a positive electrode and a negative electrode coated with an active material on both sides of a collector, a unit cell having a laminated structure composed of a separator interposed between the positive and negative electrodes, and a separator film for continuously winding the unit cells, And is mounted on a receiving portion of the case;
Wherein the innermost unit cell and the outermost unit cell of the electrode assembly have a laminated structure in which electrodes of different polarities are independently located at both ends of the unit cell;
Wherein the unit cells except for the innermost unit cell and the outermost unit cell have a laminated structure in which electrodes having the same polarity are independently positioned at both ends of the unit cell. The unit cell according to claim 1, wherein the unit cells except for the innermost unit cell and the outermost unit cell include a unit cell in which an anode is located at both ends and a unit cell in which a cathode is located at both ends, . The battery cell according to claim 1, wherein the number of unit cells of the electrode assembly is an even number. The battery cell according to claim 3, wherein the outermost electrodes of the electrode assembly have the same polarity. The battery cell according to claim 4, wherein the outermost electrodes have a negative polarity. The battery cell according to claim 1, wherein the number of unit cells of the electrode assembly is an odd number. The battery cell according to claim 6, wherein the outermost electrodes of the electrode assembly have different polarities. The method according to claim 1, wherein the electrode assembly includes a first unit cell located at the innermost position and an n-1 th unit cell and an n th unit cell, And each of the plurality of battery cells is sequentially wound so as to be positioned on the outermost side thereof. [9] The method of claim 8, wherein when the number n is an even number, a spacing corresponding to a size of the unit cell is formed between the first unit cell and the second unit cell on the pre- And the n-th unit cells are positioned such that the electrodes of the same polarity are oriented in the same direction. [9] The method of claim 8, wherein when n is an odd number, a spacing corresponding to a size of the unit cell is formed between the first unit cell and the second unit cell on the separating film before winding, Wherein the n-th unit cell and the n-th unit cell are positioned so that the electrodes of different polarities are oriented in the same direction. The battery cell according to claim 1, wherein the unit cells have the same thickness. The battery cell according to claim 1, wherein the unit cells having the electrodes of the same polarity and the electrodes of the same polarity as the unit cells having the electrodes of different polarities located at both ends are different in thickness from each other. 13. The battery cell according to claim 12, wherein the unit cells have the same coating amount of the positive electrode active material or negative electrode active material on one surface of the current collector. The battery cell according to claim 1, wherein the unit cells have the same width and length. The battery cell according to claim 1, wherein the unit cells have different widths and / or lengths. The battery cell according to claim 1, wherein the battery case comprises a cylindrical or rectangular can, and a cap mounted on an open upper end of the can. The battery cell according to claim 1, wherein the battery case is a pouch-shaped case of a laminate sheet including a resin layer and a metal layer. The battery cell according to claim 1, wherein the battery cell is a lithium secondary battery. [3] The battery cell of claim 1, wherein the separator and / or the separator film is an oil / inorganic composite porous SRS (Safety-Reinforcing Separators) separator. A device comprising at least one battery cell according to claim 1. 21. The device of claim 20, wherein the device is any one selected from the group consisting of a cell phone, a tablet computer, a notebook computer, a power tool, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, Device.

Images