KR101684315B1 - Battery Cell Comprising Unit Cells Having Different Electrode Structures - Google Patents

Abstract

The present invention relates to an electrode assembly including a positive electrode and a negative electrode coated with an active material on a current collector, unit cells 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. Is mounted on the receiving portion of the battery case; Wherein the first unit cell is located at the center of the electrode assembly with respect to the stacking direction of the unit cells and the n-1 th unit cell is located at the center of the electrode assembly, The unit cell and the n-th unit cell are sequentially wound from the first unit cell to the n-th unit cell so that the unit cell and the n-th unit cell are located at the outermost periphery of the electrode assembly, respectively; Wherein the n-th unit cell and the (n-1) th unit cell have electrodes with different polarities located at both ends of the unit cell, and the remaining unit cells have independent electrodes having the same polarity positioned at both ends of the unit cell The battery cell includes:

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.

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, electrode assemblies having an advanced structure, such as the jelly-roll type and stack type mixed structure, have been proposed, in which unit cells having a predetermined unit of positive and negative electrodes stacked with a separator interposed therebetween are placed on a separation film A stack / folding type electrode assembly having a structure in which the electrodes are sequentially wound in a state where they are positioned has been developed.

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

1, the electrode assembly 100 includes unit cells 120, 140 and 160 having a cathode-separator-anode-separator-cathode structure and unit cells 110, 140 and 160 having a cathode-separator-cathode- The separation films 180 are disposed between the unit cells 110, 120, 130, 140, 150, 160, and 170 of the electrode assembly 100, 120, 130, 140, 150, 160, and 170 in which electrode terminals are not formed.

The electrode assembly 100 is manufactured by arranging the unit cells 110, 120, 130, 140, 150, 160, 170 on the separation film 180 and winding the separation film 180, The positive electrode 111 on the uppermost stage and the lowermost anode 171 of the electrode assembly 100 are coated with active material on only one side of the current collector in the inward direction of the electrode assembly 100 and the other side of the positive electrode collector faces the separating film 180 .

Therefore, the electrode assembly 100 includes nine anodes 103, ten cathodes 102, two anode faces 111 and 171, fourteen separators 101, and one separator film 180 .

However, in the case of such a stack / folding type electrode assembly, each unit cell generally has a structure in which electrodes having the same polarity are located at both ends of the unit cell. In this case, , A large amount of current collector and an inactive material such as a separator in the same volume, the energy density is not satisfied in proportion to the thickness of the battery cell, and there is a limitation in improving the overall capacity of the battery cell .

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, as will be described later, include a unit cell having a structure in which electrodes of different polarities are located at both ends of a unit cell at the outermost periphery of the electrode assembly, The number of separators and current collectors as a whole is reduced compared with a conventional battery cell having only a unit cell having a structure in which electrodes of the same polarity are located at both ends of the unit cell. It is possible to increase the application amount of the active material of the unit cell by the thickness of the unit cell, so that it is possible to manufacture a battery having a higher energy density, which has higher capacity characteristics than the same volume. Thus, 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 a current 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, Is mounted on the receiving portion of the housing;

Wherein the first unit cell is located at the center of the electrode assembly with respect to the stacking direction of the unit cells and the n-1 th unit cell is located at the center of the electrode assembly, The unit cell and the n-th unit cell are sequentially wound from the first unit cell to the n-th unit cell so that the unit cell and the n-th unit cell are located at the outermost periphery of the electrode assembly, respectively;

Wherein the n-th unit cell and the (n-1) th unit cell have electrodes with different polarities located at both ends of the unit cell, and the remaining unit cells have independent electrodes having the same polarity positioned at both ends of the unit cell .

That is, since the battery cell according to the present invention includes unit cells formed of a structure in which electrodes having different polarities are located at both ends of a unit cell, for example, a cathode-separator-cathode, Compared with a battery cell having unit cells having structures located at both ends of the cell, for example, a unit cell composed of a positive electrode-separator-negative electrode-separator-positive electrode or a negative electrode-separator-positive electrode- It is possible to increase the application amount of the active material of each unit cell by a reduced thickness when manufacturing battery cells of the same volume so that a battery of high energy density having higher capacity characteristics than the same volume can be manufactured .

Hereinafter, the configuration of the battery cell according to the present invention will be described in more detail.

In one specific example, the electrodes positioned at the outermost portion of the electrode assembly, that is, the (n-1) th unit cell and the n th unit cell, are formed such that only one surface of the current collector facing the electrode of the opposite polarity And the electrodes other than the outermost electrodes may be coated with an active material on both sides of the collector in order to exhibit excellent capacity.

In one specific example, the unit cells other than the n-th unit cell and the (n-1) th unit cell are not limited as long as the electrodes of the same polarity are located at both ends of the unit cell. Specifically, And a unit cell having a structure in which the cathode is located at both ends. The nth unit cell and the (n-1) th unit cell may be arranged such that the positions of the electrode terminals are opposite to each other.

Therefore, the battery cell according to the present invention is a unit cell of an electrode assembly, in which a structure in which electrodes of different polarities are located at both ends of a unit cell, a structure in which an anode is located at both ends of the unit cell, And the like.

Meanwhile, the electrode assembly may include n odd number of unit cells, and the number of the unit cells may be set in consideration of the shape and size of the device and the capacity of the battery cell. Specifically, n is an integer of 3 or more, May be an integer of 5 or more.

When the number of unit cells is an odd number, the polarities of the outermost electrodes may be the same. This is because the arrangement of the unit cells should be such that the anode and the cathode are alternately arranged in a wound state, And the unit cells having the structure in which the electrodes are located at both ends of the unit cell exist as the n-th unit cell and the (n-1) th unit cell.

At this time, the polarities of the outermost electrodes may vary according to the arrangement of the first unit cells, and both of the positive and negative electrodes may be, but are not limited to, an anode.

In one specific example, the electrode assembly is wound around the first unit cell, so that the second unit cell and the third unit cell are positioned on both sides of the first unit cell, A separation region corresponding to the size of the unit cell may be formed between the first unit cell and the second unit cell so that the separation membrane can be positioned.

As described above, it is preferable that the n-1 th unit cell and the n th unit cell are provided with an active material on only one surface of the current collector facing the electrode of the opposite polarity in the wound state. Therefore, The separator film may have a structure in which an active material is not coated on one surface of the collector facing the separator film.

Meanwhile, the unit cells may have the same thickness, or the thicknesses of the n-th unit cell and the (n-1) th unit cell and the remaining unit cells may be different from each other.

Specifically, an n-th unit cell and / or an n-th unit cell having a structure in which electrodes of different polarities are located at both ends of a unit cell, So that all of the unit cells can have the same thickness regardless of the configuration.

On the other hand, it is possible to uniformly add the active material corresponding to the thickness of the collector and the separation membrane, which is reduced compared to the conventional battery cell, to all the unit cells constituting the battery cell, -1 unit cell, and the remaining unit cells may have different thicknesses.

When the unit cells are uniformly added to all the unit cells as described above, the amount of the positive electrode active material or the negative electrode active material applied to one surface of the current collector of each unit cell may be the same, The same amount of active material can be applied to one surface of the current collector without dividing the configuration of the unit cell in the manufacturing process of the cell because it is possible to reduce manpower and time required for the process.

The unit cells may have the same width and length, but the present invention is not limited thereto. The width and / or length of the unit cells may be varied depending on the type and shape of the device on which the battery cell is mounted. They may be made 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.

The battery cell according to the present invention is manufactured by attaching the electrode assembly having the above structure to the battery case, and the battery case is not limited to a structure including a cylindrical or square can and a cap mounted on the open upper end portion of the can Or may be a pouch-shaped 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. In the present invention, the separation film is also included as the same function as the separation membrane.

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 and the separation film are interposed between the anode and the cathode, and generally an insulating thin film having high ion permeability and mechanical strength can be used. Such separation membranes and separation films include, for example, olefin-based polymers such as polypropylene, which is chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like can be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separation membrane and a separation film.

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 the advantage of suppressing an increase in thickness of the cell due to swelling at the time of chemical conversion compared with the case of using a conventional separator, 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 has a plurality of uniform pore structures formed in both the active layer and the polyolefin-based separator substrate, and the lithium ion is smoothly moved through the pores, and a large amount of electrolyte is filled, Therefore, the performance of the battery can be improved at the same time.

The organic / inorganic composite porous separator composed of the inorganic particles and the binder polymer does not have high temperature heat shrinkage due to the heat resistance of the inorganic particles. Therefore, in the electrochemical device using the organic / inorganic composite porous film as a separator, even if the separator ruptures in the cell due to internal or external factors such as high temperature, overcharging, external impact, etc., The electrodes are hardly short-circuited completely, and even if a short circuit occurs, the short-circuited area is prevented from being greatly enlarged, thereby improving the safety of the battery.

Since the organic / inorganic composite porous separation membrane is formed by coating directly on the polyolefin-based separation membrane, the pores on the surface of the polyolefin-based membrane substrate and the active layer exist as anchoring mutually, so that the active layer and the porous substrate are physically and firmly bonded . Accordingly, not only the problems of mechanical properties such as brittleness can be improved, but also the interfacial adhesion between the polyolefin-based separator base material and the active layer is excellent and the interface resistance is reduced. In the organic / inorganic composite porous separator, the organic / inorganic complex active layer and the porous substrate are chemically bonded to each other, and the pore structure existing in the porous substrate remains unaffected by the active layer, It can be seen that a uniform pore structure due to the inorganic particles is formed in itself. Such a pore structure is filled with a liquid electrolyte to be injected at a later stage, which results in a significant reduction in interfacial resistance between the inorganic particles and between the inorganic particles and the binder polymer.

The organic / inorganic composite porous separation membrane can exhibit excellent adhesive force characteristics by controlling the content of inorganic particles and binder polymer in the separation membrane, so that the battery assembly process can be easily performed.

In the organic / inorganic composite porous separator, one of the active layer components formed on the surface of the polyolefin-based separator substrate and / or the pores of the substrate is an inorganic particle ordinarily used in the art. The inorganic particles enable the formation of voids between the inorganic particles to form micropores and serve as a kind of spacer capable of maintaining the physical shape. In addition, since the inorganic particles generally have a property that their physical properties do not change even at a high temperature of 200 DEG C or more, the formed organic / inorganic composite porous film has excellent heat resistance.

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.

For the reasons stated above, the inorganic particles are preferably high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transporting ability, or mixtures thereof Do.

The piezoelectricity inorganic particle means a non-conductive material at normal pressure or a material having electrical conductivity due to a change in internal structure when a certain pressure is applied, and exhibits a high permittivity with a dielectric constant of 100 or more, The charge is generated in the case of applying tensile or compressive force, so that one side is charged positively and the other side is negatively charged, thereby generating a potential difference between both sides.

When inorganic particles having the above-described characteristics are used as the porous active layer component, if an internal short-circuit of both electrodes occurs due to an external impact such as local crush or nail, due to the inorganic particles coated on the separator, Not only do not directly contact but also cause a potential difference in the particle due to the piezoelectricity of the inorganic particles. As a result, the electron transfer between the two electrodes, that is, the flow of a minute current, The safety can be improved.

Examples of the inorganic particles having piezoelectricity include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT) hafnia (HfO ₂ ), or mixtures thereof.

The inorganic particles having the lithium ion transferring ability refer to inorganic particles that contain a lithium element but do not store lithium but have a function of transferring lithium ions. The inorganic particles having lithium ion transferring ability exist in the particle structure Since lithium ions can be transferred and transferred due to a kind of defect, the lithium ion conductivity in the battery can be improved and the battery performance can be improved.

Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li _3.25 Ge (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as _0.25 P _0.75 S ₄ , Li ₃ lithium nitride such as _{N (Li x N y, 0} <x <4, 0 <y <2), Li 3 PO 4 -Li 2 Li x (SiS 2 based glass, such as _{S-SiS 2 Si y S z} , 0 <x <3, 0 < y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 P 2 , such as S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof, but are not limited thereto.

Examples of inorganic particles having a dielectric constant of 5 or more include SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC, But is not limited thereto. When the above-mentioned high-permittivity inorganic particles, piezoelectric particles, and inorganic particles having lithium ion-transporting ability are mixed, their synergistic effect can be doubled.

The organic / inorganic composite porous separator of the present invention can control the pore structure of the active layer, as well as the pores contained in the separator substrate, by adjusting the size of the inorganic particles, the content of the inorganic particles, and the composition of the inorganic particles and the binder polymer, And the pore size and porosity can be adjusted together.

The size of the inorganic particles is not limited, but is preferably in the range of 0.001 to 10 mu m for the formation of a film of uniform thickness and a suitable porosity. In the case where the thickness is less than 0.001 탆, the dispersibility of the organic / inorganic composite porous separator is lowered, and it is difficult to control the physical properties of the organic / inorganic composite porous separator. When the thickness exceeds 10 탆, And the excessively large pore size increases the probability of an internal short circuit occurring during charging and discharging of the battery.

The content of the inorganic particles is not particularly limited, but is preferably in the range of 50 to 99% by weight, more preferably 60 to 95% by weight, based on 100% by weight of the mixture of the inorganic particles constituting the organic / inorganic composite porous separator and the binder polymer Do. If the amount is less than 50% by weight, the content of the polymer is excessively increased, and the pore size and porosity may be decreased due to the reduction of the void space formed between the inorganic particles, resulting in deterioration of the final battery performance. On the contrary, when the content is more than 99% by weight, the mechanical properties of the final organic / inorganic composite porous membrane are deteriorated due to the weak adhesive force between the inorganic materials because the polymer content is too small.

In the organic / inorganic composite porous separator according to the present invention, the other of the active layer constituents formed on the surface of the polyolefin-based membrane base material and / or the pores of the above-described substrate is a polymer commonly used in the art. Particularly, it is possible to use a glass transition temperature (Tg) as low as possible, preferably in the range of -200 to 200 ° C. This is because the mechanical properties such as flexibility and elasticity of the final film can be improved. The polymer faithfully fulfills the role of a binder to connect and stably fix the inorganic particles and particles, the inorganic particles and the surface of the separator substrate, and the pores of the separator membrane, thereby improving the mechanical properties of the final organic / inorganic composite porous separator Thereby preventing degradation.

In addition, although the binder polymer does not necessarily have ion conductivity, the performance of the electrochemical device can be further improved by using a polymer having ion conductivity. Therefore, it is preferable that the binder polymer has a high permittivity constant.

In fact, since the degree of dissociation of the salt in the electrolyte depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the polymer, the better the salt dissociation in the electrolyte of the present invention. The dielectric constant of the polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), more preferably 10 or more.

In addition to the above-mentioned functions, the binder polymer may be gelled upon impregnation with a liquid electrolyte to exhibit a high degree of swelling of the electrolyte. In fact, when the binder polymer is a polymer having an excellent electrolyte impregnation rate, the electrolyte injected after assembling the battery is impregnated with the polymer, and the polymer having the absorbed electrolyte has electrolytic ion conduction capability. Therefore, the performance of the electrochemical device can be improved compared to the conventional organic / inorganic composite electrolyte. In addition, compared with the conventional hydrophobic polyolefin-based separator, wetting of the electrolyte for a battery is improved, and polarity electrolytic solution for a battery, which has not been used conventionally, can be applied. In addition, when the polymer is a polymer that can be gelled when the electrolyte is impregnated, the gelled organic / inorganic composite electrolyte can be formed by allowing the injected electrolyte and the polymer to react with each other and gel. The thus formed electrolyte is easier to manufacture than the conventional gel type electrolyte, and exhibits high ion conductivity and electrolyte impregnation rate, thereby improving the performance of the battery. Therefore, if possible, a polymer having a solubility index of 15 to 45 MPa &lt; 1/2 &gt; is preferable, and 15 to 25 MPa &lt; 1/2 &gt; and 30 to 45 MPa & When the solubility index is less than 15 MPa &lt; 1/2 &gt; and more than 45 MPa &lt; 1/2 &gt;, it becomes difficult to swell by a common liquid electrolyte for a battery.

Examples of usable binder polymers include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotylchlorethylene, polymethylmethacrylate, Polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate (cellulose acetate), cellulose acetate Cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, hydroxypropylcellulose, hydroxypropylcellulose, hydroxypropylcellulose, Cyanoethyl Acrylonitrile-styrene-butadiene copolymer, polyimide, or a mixture thereof, and the like may be used as the binder resin. The binder may be selected from the group consisting of acrylonitrile-styrene-butadiene copolymer, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile- However, it is not limited thereto, and any material including the above-mentioned characteristics may be used alone or in combination.

The composition ratio of the inorganic particles and the binder polymer as the active layer component is not particularly limited, but can be adjusted within a range of 10:90 to 99: 1 wt.%, And is preferably in a range of 80:20 to 99: 1 wt. When the ratio is less than 10: 90% by weight, the content of the polymer is excessively increased, resulting in a decrease in the pore size and porosity due to the reduction of the void space formed between the inorganic particles, , The mechanical properties of the final organic / inorganic composite porous membrane may be deteriorated due to the weakening of the adhesion between the inorganic materials because the polymer content is too small.

The active layer of the organic / inorganic composite porous separator may further include other commonly known additives in addition to the inorganic particles and polymers described above.

In the organic / inorganic composite porous separator, a substrate coated with a mixture of inorganic particles and a binder polymer as the active layer constituent may be a polyolefin-based separator commonly used in the art. Examples of the polyolefin-based separation membrane component include high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene or derivatives thereof.

The thickness of the polyolefin-based separator base material is not particularly limited, but is preferably in the range of 1 to 100 mu m, more preferably in the range of 5 to 50 mu m. If it is less than 1 탆, it is difficult to maintain the mechanical properties, and when it exceeds 100 탆, it can act as a resistive layer.

The pore size and porosity in the polyolefin-based membrane substrate are not particularly limited, but the pore size is preferably in the range of 10 to 95% and the pore size (diameter) is preferably in the range of 0.1 to 50 μm. When the pore size and the porosity are less than 0.1 μm and less than 10%, respectively, they act as resistance layers. If the pore size and porosity are more than 50 μm and 95%, it becomes difficult to maintain the mechanical properties. In addition, the polyolefin-based membrane substrate may be in the form of fibers or membranes.

The organic / inorganic composite porous separation membrane of the present invention formed by coating a mixture of inorganic particles and a binder polymer on a polyolefin separation membrane substrate includes not only pores in the separation membrane substrate itself but also inorganic particles Both the substrate and the active layer form a pore structure. The pore size and porosity of the organic / inorganic composite porous separation membrane depend mainly on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 μm or less are used, the pores formed also show 1 μm or less. Such a pore structure is filled with an electrolyte solution to be injected at a later stage, and the filled electrolyte serves as an ion transfer function. Therefore, the pore size and porosity are important factors for controlling the ionic conductivity of the organic / inorganic composite porous separator.

The thickness of the active layer on which the pore structure is formed by coating with the above mixture on the polyolefin separator substrate is not particularly limited, but is preferably in the range of 0.01 to 100 mu m. The pore size and the porosity of the active layer are preferably in the range of 0.001 to 10 탆 and 5 to 95%, respectively, but are not limited thereto.

Preferably, the pore size and the porosity of the organic / inorganic composite porous separation membrane are in the range of 0.001 to 10 탆 and 5 to 95%, respectively. In addition, the thickness of the organic / inorganic composite porous separator is not particularly limited, and can be adjusted in consideration of cell performance. More preferably in the range of 1 to 100 mu m, and particularly preferably in the range of 1 to 30 mu m.

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 n-th unit cell and the n-1-th unit cell located at the outermost position in the electrode assembly including n unit cells are connected to both ends It is possible to reduce the number of separators and current collectors as a whole as compared with a battery cell having a structure in which electrodes of the same polarity are conventionally located at both ends of the unit cell, Therefore, when a battery cell of the same volume is manufactured, the application amount of the active material of the unit cell can be increased by a reduced thickness, and an effect of manufacturing a battery of a high energy density having a capacity characteristic higher than that of the same volume have.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram 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;
FIG. 3 is a schematic view schematically showing the structure of some unit cells of FIG. 2; FIG.
FIG. 4 is a schematic view schematically showing the structure of a battery cell manufactured according to the manufacturing method of FIG. 2. FIG.

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 showing a method of manufacturing an electrode assembly for a battery cell according to an embodiment of the present invention, and FIG. 3 is a schematic view schematically showing the structure of a unit cell of FIG.

Referring to FIGS. 2 and 3, the electrode assembly 200 includes a plurality of unit cells 210, 220, 230, 240, and 250 having a polarity different from that of the unit cells 210, The unit cells 260 and 270 having the structures located at both ends of the cell are alternately arranged on the separation film 280 and the separation film 280 is wound.

Specifically, the electrode assembly 200 includes seven unit cells 210, 220, 230, 240, 250, 260 and 270, and the sixth unit cell 260 and the seventh unit cell 270, 220, 230, and 240 from the first unit cell 210 to the fifth unit cell 250. The five unit cells 210, 220, 230, and 240 are formed in a stacked structure having electrodes of different polarities positioned at both ends of the unit cell. And 250 are structured such that electrodes having the same polarity are located at both ends of the unit cell.

The outermost electrodes of the second unit cell 220 and the third unit cell 230 of the unit cells 210, 220, 230, 240, 250, 260, and 270 are cathodes, The outermost electrode 210, the fourth unit cell 240, and the fifth unit cell 250 are configured as positive electrodes.

The sixth unit cell 260 and the seventh unit cell 270 face the separating film 280 with the anodes 261 and 271 facing toward the bottom. And is positioned on the separation film from the second unit cell 220 to the seventh unit cell 270.

The sixth unit cell 260 and the seventh unit cell 270 are arranged such that the positions of the electrode terminals are opposite to each other.

The sixth unit cell 260 and the seventh unit cell 270 located at the outermost side of the electrode assembly 200 are disposed on the outermost side of the electrode assembly 200, Are arranged such that the anodes 261 and 271 face the separating film 280 toward the bottom, respectively.

The sixth unit cell 260 positioned at the outermost portion of the electrode assembly 200 is disposed on the anode 261 that is the outermost electrode of the electrode assembly 200 with the separator 263 therebetween, The active material 261b is added only to one surface of the current collector 261a facing the cathode 262 and the active material is not provided on the other surface of the current collector 261a facing the separation film 280 .

Similarly, the seventh unit cell 270 positioned at the outermost of the electrode assembly 200 is disposed on the anode 271, which is the outermost electrode of the electrode assembly 200, with the separator 273 therebetween, The active material 271b is added only to one surface of the current collector 271a facing the cathode 272 and no active material is added to the other surface of the current collector 271a facing the separation film 280. [

Accordingly, the other surfaces of the current collectors 261a and 271a to which the active material is not applied are positioned at the outermost portions of the electrode assembly 200. Accordingly, when the battery cell is damaged by the conductive material, the active materials 261b and 262b 262c, 271b, 272b, and 272c are directly in contact with the conductive material, heat generation and fire can be prevented, and safety can be improved.

The electrode assembly 200 is manufactured by winding the first unit cell 210 in the counterclockwise direction 282 from the first unit cell 210 to the seventh unit cell 270 so that the first unit cell 210 is located at the innermost position .

The first unit cell 210 and the second unit cell 220 are spaced apart from each other by a distance 281 corresponding to the size of the unit cell, The separation film 280 is interposed between the anode 212 positioned on the upper surface of the first unit cell 210 and the cathode 232 positioned on the upper surface of the third unit cell 230. [

Specifically, the first unit cell 210 moves to the spaced-apart portion 281 between the first unit cell 210 and the second unit cell 220 in an inverted state during the winding process, The anode 211 positioned on the lower surface of the unit cell 210 is wound so as to face the cathode 222 located on the upper surface of the second unit cell 220 and the separation film 280 therebetween.

The first unit cell 210 and the second unit cell 220 facing each other with the separation film 280 therebetween are simultaneously wound by the separation film 280 so that the first unit cell 210 The anode 212 positioned on the upper surface of the third unit cell 230 faces the cathode 232 located on the upper surface of the third unit cell 230 with the separation film 280 therebetween.

The process progresses sequentially to the seventh unit cell 270. Thus, the first unit cell 210 is located on the innermost side and the sixth unit cell 260 and the seventh unit cell 270 The electrode assembly 200 is completed.

FIG. 4 is a schematic view schematically showing the structure of the electrode assembly manufactured according to the above-described manufacturing method.

Referring to FIG. 4 together with FIG. 2, the sixth unit cell 260 and the seventh unit cell 270, each having a structure in which electrodes of different polarities are located at both ends of the unit cell, Thereby constituting one of the unit cells.

The electrode assembly 200 includes seven unit cells 210, 220, 230, 240, 250, 260 and 270. The first unit cell 210 of the electrode assembly 200 includes positive electrodes 211 and 212 And the polarities of the outermost electrodes 261 and 271 of the electrode assembly 200 are equal to each other as an anode.

Meanwhile, when the cathode of the first unit cell 210 faces the bottom, the outermost electrodes of the electrode assembly 200 may be formed of a cathode.

The electrode assembly 200 thus configured includes eight positive electrodes, nine negative electrodes, two positive electrode sections, and twelve separators.

As a result, the number of separation membranes, which are inactive materials, is reduced and the number of the positive and negative electrodes is reduced compared to a battery cell composed of only unit cells having a structure in which electrodes of the same polarity are located at both ends of the unit cell. The total quantity is also reduced, so that as much as the amount of the active material corresponding to the thickness of the reduced inert material can be added to each electrode, consequently, the overall capacity of the battery cell can be increased.

As a result, the number of separation membranes, which are inactive materials, is reduced and the number of the positive and negative electrodes is reduced compared to a battery cell composed of only unit cells having a structure in which electrodes of the same polarity are located at both ends of the unit cell. The total amount of the active material can be reduced, and the amount of the active material corresponding to the thickness of the reduced inert material can be further added. As a result, the overall capacity and the energy density of the battery cell can be increased.

In the electrode assembly 200, electrodes having the same polarity as that of the sixth unit cell 260 and the seventh unit cell 270 structured such that electrodes of different polarities are located at both ends of the unit cell are disposed at both ends of the unit cell The first unit cell 210 to the fifth unit cell 250 of the battery cell 200 are different in overall thickness from each other. This means that the amount of the active material corresponding to the thickness of the collector and the separator, 210, 220, 230, 240, 250, 260, and 270, respectively.

Accordingly, since the application amounts of the active material on the one surface of the current collectors of the unit cells 210, 220, 230, 240, 250, 260, and 270 are all uniform, , 230, 240, 250, 260, and 270), it is possible to reduce the manpower and time required for the process, because the active material is uniformly applied to one surface of the current collector.

However, the present invention is not limited thereto. The unit cells 210, 220, 230, 240, 250, 260, and 270 of the electrode assembly 200 may have the same thickness, The sixth unit cell 260 and the seventh unit cell 270 having a structure in which the electrodes of different polarities are located at both ends of the unit cell, as well as the active material corresponding to the thickness of the collector and the separator, The sixth unit cell 260 and the seventh unit cell 270 may have the first unit cell 210 to the fifth unit cell 270 having electrodes of the same polarity positioned at both ends of the unit cell, (250). &Lt; / RTI &gt;

The structure of the battery cell according to the present invention is not limited to that described above with reference to the drawings. The battery cell has a structure in which a separation film is wrapped in a Z-shape from the lowermost unit cell to the uppermost unit cell of the electrode assembly, May be fabricated by folding cells.

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.

&Lt; Example 1 >

The electrode assembly was assembled as shown in FIGS. 2 to 4, 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.

&Lt; 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 and the battery capacity 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 cm ² ) Capacity (mAh) Energy density (Wh / L) Comparative Example 1 7 525 4053 598 Example 1 600 4164 614

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 in which the electrode of the same polarity is disposed at both ends of the unit cell, The capacity of the cell is increased by 2.7%, and the energy density is increased by 2.7%.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (20)

An electrode assembly including a positive electrode and a negative electrode coated with an active material on a current 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, Is mounted on the receiving portion of the housing;
Wherein the electrode assembly has n number of odd number of unit cells arranged on a long length of the separation film, the first unit cell is positioned at the center of the electrode assembly with respect to the stacking direction of the unit cells, The unit cell and the n-th unit cell are sequentially wound from the first unit cell to the n-th unit cell so that the unit cell and the n-th unit cell are located at the outermost periphery of the electrode assembly, respectively;
Wherein the n-th unit cell and the (n-1) th unit cell have electrodes with different polarities located at both ends of the unit cell, and the remaining unit cells have independent electrodes having the same polarity positioned at both ends of the unit cell Lt; / RTI &gt;
The electrodes located at the outermost portions of the electrode assembly are provided with active materials only on one surface of the current collector facing the electrodes of the opposite polarity in the wound state and the internal electrodes except for the electrodes located at the outermost portions of the electrode assembly are connected to the current collector Active materials are applied on both sides,
And the unit cells other than the n-th unit cell and the (n-1) th unit cell of the electrode assembly include a unit cell having a structure in which an anode is located at both ends and a unit cell having a structure in which a cathode is located at both ends Battery cell. delete delete delete The battery cell according to claim 1, wherein the outermost electrodes of the electrode assembly have the same polarity. The battery cell according to claim 5, wherein the polarity of the outermost electrodes is an anode. [3] The apparatus of claim 1, wherein the first unit cell and the second unit cell are formed with spaced apart portions corresponding to the size of the unit cell on the pre-wind separation film, and the n-th unit cell and the n- And the electrodes of the same polarity are positioned so as to face in the same direction. 8. The battery cell according to claim 7, wherein the n-th unit cell and the (n-1) th unit cell are arranged such that the electrode terminals are positioned at opposite positions. The battery cell according to claim 1, wherein n is an integer of 5 or more. The battery cell according to claim 1, wherein the unit cells have the same thickness. The battery cell according to claim 1, wherein the n-th unit cell and the (n-1) th unit cell and the remaining unit cells have different thicknesses. 12. The battery cell according to claim 11, wherein the unit cells have the same coating amount of the cathode active material or the anode 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. [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. 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. A device comprising at least one battery cell according to claim 1. 20. The device of claim 19, 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.

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