KR20160108116A - Battery Cell Comprising a Separator with Enhanced Adhesive Property - Google Patents

Abstract

The present invention relates to a battery cell of which battery case embeds an electrode assembly including a positive electrode, a negative electrode, and a separation film interposed between the positive and negative electrodes. The separation film includes a porous polymer member and an organic/inorganic porous coating layer formed on at least one surface of the porous polymer member. The organic/inorganic porous coating layer includes: inorganic particles including a mixture of a metal oxide and a metal hydroxide; a PVdF-HFP polymer binder (PHFP high) having a high content of hexafluoropropylene (HFP); and a PVdF-HFP polymer binder having a low content of HFP. Adhesive force between the separation film and the positive or negative electrode is not less than 15gf/25mm.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell including a separator having enhanced adhesion,

The present application claims the benefit of priority based on Korean Patent Application No. 10-2015-0030848, filed on May 5, 2015, and all contents disclosed in the Korean patent application are incorporated herein by reference.

The present invention relates to a battery cell including a separator having enhanced adhesion.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operational potential, long cycle life, Batteries have been commercialized and widely used.

However, since such a lithium secondary battery has a problem in safety, attempts have been made to solve it.

Specifically, when the adhesive force between the electrode and the separator is weak, short-circuiting may occur between the electrodes due to the separation of the separator and the electrode during charging and discharging of the battery. In this case, locally excessive current flows to generate heat, there is a problem. In addition, when the adhesive force is weak, the interfacial resistance increases due to the widening between the electrodes, and the electrode can be bent, resulting in a safety problem.

In order to solve the safety problem, a separator has been proposed in which a porous coating layer is formed by coating a slurry containing an excess of inorganic particles and a polymer binder on at least one surface of a porous substrate having a plurality of pores. However, this separation membrane is also difficult to exhibit sufficient adhesion with the electrodes, and sufficient adhesion can be exhibited only if the porous coating layer is thickly formed. In this case, however, the overall resistance increases, the volume of the electrode assembly itself increases, There was a problem.

In recent years, a new type of battery cell is required due to a trend change of a slim type or various designs.

There is a problem in that the capacity of the battery cell must be reduced or the design of the device must be changed to a larger size in order to make the battery cell into a novel structure in consideration of the design of the applied device.

Therefore, in order to overcome such a problem, some prior arts may form a battery pack by stacking battery cells of different sizes. However, since such a battery pack has a structure of stacking battery cells, the stacked battery cells can not share an electrochemical reaction, resulting in a thicker battery pack. As a result, the battery capacity can be reduced, In such a design change process, the electrical connection method becomes complicated, making it difficult to manufacture a battery cell satisfying a desired condition.

Accordingly, it has been required to develop an unshaped battery cell in which the shape of the electrode assembly itself is changed according to the shape of the device to which the battery cell is applied. In order to manufacture the battery cell, the separator is cut after lamination of electrodes and separator cutting work was essential. However, in this case, if the adhesive force between the electrode and the separator is low, it is difficult to accurately cut the separator while the separator is being pushed in the separator cutting process, and the above-described short- there was.

Accordingly, there is a high need for a battery cell capable of further improving the adhesion between the electrode and the separator to solve the above problems.

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

The inventors of the present application are at the end of extensive research and various experiments in depth, the metal oxide and the inorganic particles containing a mixture of a metal hydroxide and, hexafluoropropylene (HFP) content is high PVdF-HFP polymer binder ( 'P _{HFP high} ') and a PVdF-HFP polymer binder having a low HFP content (' P _{HFP low} ') is formed on at least one surface of the porous polymer base material, the organic / inorganic porous coating material layer It has been found that even when the porous polymer substrate is coated with a thin thickness, the polymer can exhibit excellent adhesion with an electrode and can improve the heat shrinkage ratio of the separator. Thus, the present invention has been accomplished.

Therefore, in the battery cell according to the present invention,

An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,

Wherein the separation membrane comprises a porous polymer base material and an organic or inorganic porous coating layer formed on at least one side of the porous polymer base material,

The organic or inorganic porous coating layer comprises inorganic particles including a mixture of a metal oxide and a metal hydroxide, a PVdF-HFP polymer binder ('P _{HFP high} ') having a high hexafluoropropylene (HFP) content, and a PVdF -HFP polymer binder ('P _{HFP low} '),

The adhesive force between the separator and the anode or the cathode is 15 gf / 25 mm or more.

At this time, the organic or inorganic porous coating layer may have a thickness of 0.5 micrometers to 5 micrometers, more specifically, 1 micrometer to 3 micrometers, based on the cross section of the porous polymer substrate.

Such an organic-inorganic porous coating layer having the above-mentioned thickness range is an optimal range for imparting heat resistance to the separator without increasing the internal resistance of the battery cell. If the porous inorganic coating layer is too thin, it can not add heat resistance to the separator The adhesive force can not be obtained beyond the desired value. On the contrary, when the thickness is too large, the overall volume increases, the volume-to-volume ratio decreases, and the internal resistance can not be obtained.

As described above, the inventors of the present application have found that the separation membrane according to the present invention, that is, inorganic particles including a mixture of a metal oxide and a metal hydroxide, and a PVdF-HFP polymer binder having a high hexafluoropropylene (HFP) (&_Quot; P _{HFP high} ") and a PVdF-HFP polymer binder having a low HFP content ('P _{HFP low} ') was formed on at least one surface of the porous polymer substrate, The adhesion force between the separator and the electrode can be improved to 15 gf / 25 mm or more, specifically 15 gf / 25 mm to 30 gf / 25 mm even if the organic / inorganic porous coating layer is formed to have a small thickness. It is confirmed that the safety of the battery cell can be improved.

Further, when metal oxides and metal hydroxides are used together, the particle size can be formed in two forms to maximize the packaging per unit area, and thermal shrinkage of the separator can be further improved.

In the present specification, the term 'PVdF-HFP polymer binder' refers to a polymeric binder composed of vinylidene fluoride (VdF), which comprises a constituent unit derived from vinylidene fluoride (VdF) and a constituent unit derived from hexafluoropropylene The molecular weight of the 'PVdF-HFP polymer binder' according to the present invention may be 100,000 g / mol to 1,000,000 g / mol, and more specifically 200,000 g / mol to 700,000 g / mol.

In the present specification, 'P _{HFP high} ' means a PVdF-HFP polymer binder having a relatively _high HFP content. Specifically, 'P _{HFP high} ' is contained in the polymer in an amount of 8 to 20 wt% Specifically, it may contain 12 to 20% by weight of HFP.

In the present specification, 'P _{HFP low} ' means a PVdF-HFP polymer binder having a relatively _low HFP content. Specifically, 'P _{HFP low} ' is contained in the polymer in an amount of 3 to 15 wt% In detail, it may contain 3 to 8% by weight of HFP.

Of course, HFP content of 'P _{HFP high'} of the HFP content of the 'P _{HFP low'} in the mixture according to the invention doedoe included to satisfy the above range, in the HFP content of the 'P _{HFP high'} 'P _{HFP low'} HFP More than the content. Specifically, HFP content of the difference between P and P _{high HFP HFP low} preferably includes HFP the _{high HFP} P, based on the weight of the polymeric binder, each lot more than 5% by weight of _HFP than P _low.

When the content difference is less than 5% by weight, it is not preferable because it can not exhibit a desired degree of adhesion to be obtained by mixing two types of PVdF-HFP polymer binders, that is, an adhesive force of 15 gf / 25 mm or more.

The P _{HFP high} and P _{HFP low} may be mixed at a weight ratio of 1: 3 to 1:20.

If the P _{HFP low} is too _low , the permeation time of the separator deteriorates, thereby increasing the resistance and adversely affecting the battery characteristics. If the P _{HFP low} is included too much, There is a problem in that the adhesion between the electrodes is weakened and the electrodes are short-circuited due to charging or discharging of the cells or pilling when cutting the separator, which is not preferable.

Further, in addition to the above-mentioned PVdF-HFP polymer binder, the organic or inorganic porous coating layer may include other kinds of organic polymeric binders to the extent that the purpose of the present invention is met. For example, polyvinylidene fluoride- Polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ), Polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propyl cellulose, Cellulose acetate propionate, cyano And is made up of cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. And mixtures of two or more thereof. At this time, the different kind of organic polymer binder may be contained in an amount of 0 to 30% by weight based on the total weight of the polymeric binder contained in the organic / inorganic porous coating layer.

On the other hand, as another component for forming the organic porous coating layer, the inorganic particles may be a mixture of a metal oxide and a metal hydroxide, wherein the metal hydroxide may be contained in an amount of 0.01 to 0.3 mol per 1 mol of the metal oxide.

If the amount of the metal hydroxide is less than 0.01 mol per 1 mol of the metal oxide, the effect of improving the heat shrinkage of the separator of the present invention to a desired extent can not be obtained.

The types of the metal oxides and the metal hydroxides are not limited to whether they contain the same metal or different metals, but may specifically include one or more of the same metals. The metal is not limited as long as it can form solid oxides and hydroxides. For example, Al, Ti, Sn, Ni, Mg, Ce, Sn, Sr, Pb, Si, Zn, which may have one or more selected from the group consisting of Ba, specifically, wherein the metal is of Al, the metal oxide is Al ₂ O _3, a metal hydroxide may be AlOOH.

The average particle diameter of the metal oxide of the inorganic particles is in the range of 300 to 500 占 퐉, and the average particle diameter of the metal hydroxide may be in the range of 150 to 400 nm. In the case where the metal oxide and the metal hydroxide are contained together in different particle diameters as described above, the metal oxide can be invited to the same area, thereby improving the heat shrinkage. In order to obtain the effect of the present invention, It is preferable to include all of the hydroxides.

The total content of the inorganic particles may be in the range of 50 to 95% by weight, specifically 60 to 95% by weight, based on the total weight of the organic or inorganic porous coating layer.

If the amount is less than 50% by weight, the content of the polymeric binder is excessively increased, and the pore size and porosity are decreased due to the reduction of the void space formed between the inorganic particles, If it is contained in an amount exceeding 95% by weight, the content of the polymeric binder is too small, so that the mechanical properties of the separator itself may be deteriorated due to the weakening of the adhesion between the inorganic materials.

As can be seen from the above, the structure of the organic or inorganic porous coating layer including the inorganic particles and the PVdF-HFP polymer binder is not limited, but the organic polymer binder And interstitial volumes may be formed between the inorganic particles. Herein, the interstitial volume between the inorganic particles means a space defined by inorganic particles substantially interfaced with each other in a closed packed or densely packed structure.

On the other hand, the organic or inorganic porous coating layer can be formed by preparing a slurry for a porous coating layer using a solvent together with inorganic particles and a polymer binder, and then applying the slurry to at least one surface of the porous polymer substrate and drying. Specifically, a poor solvent (for example, ethanol) is added to a solution in which a polymer binder is dissolved in a good solvent (for example, acetone), and the resultant is applied on a porous polymer substrate By drying, the porous coating layer can be formed by the phase separation effect. In general, the organic or inorganic porous coating layer obtained by such a method has the advantages of excellent wettability and low resistance in battery operation, while there is a disadvantage in that the adhesion force is reduced due to swelling after pouring in the manufacturing process of the battery. By using the mixed PVdF-HFP polymer binder and the mixed inorganic particles as described above, it is possible to improve the heat shrinkage ratio of the separator by the maximum packaging per unit area even when the organic or inorganic porous coating layer is applied to a thin thickness have.

Further, the slurry for the porous coating layer may further contain additives commonly used in the art. Such additives may be, for example, dispersants to further improve dispersion of the inorganic particles. The dispersant functions to keep the inorganic filler in a uniformly dispersed state in the binder resin, and any one or more selected from the group consisting of an oil soluble polyamine, an oil soluble amine compound, a fatty acid, a fatty alcohol and a sorbitan fatty acid ester can be used, Specifically, it may be a high molecular weight polyamine amide carboxylic acid salt. The content of the dispersant may be 1 to 10 parts by weight based on 100 parts by weight of the inorganic particles. If the dispersant is contained in an amount of less than 1 part by weight based on 100 parts by weight of the inorganic particles, the inorganic filler easily precipitates. On the other hand, If the amount is more than 1 part by weight, there is a problem that the adhesion of the organic or inorganic porous coating layer to the porous polymer substrate is reduced, or impurities are generated by reaction with the electrolytic solution in the production of the secondary battery.

On the other hand, the porous polymer substrate that can be used in the present invention is not limited as long as it is a planar porous polymer substrate commonly used in a battery such as a porous film or a nonwoven fabric formed of various polymers. For example, the porous polymer substrate is generally used as a separator of a lithium secondary battery And a nonwoven fabric made of polyethylene terephthalate fiber. The material and the shape of the nonwoven fabric may be variously selected depending on the purpose.

The polyolefin-based porous film may be formed of a polyolefin-based polymer such as polyethylene, polypropylene, polybutylene, or polypentene, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, And the nonwoven fabric may be made of a polyolefin-based polymer or a fiber using a polymer having higher heat resistance.

The thickness of the porous polymer base material is not particularly limited, but may be in the range of 1 to 100 占 퐉, and more specifically, in the range of 5 to 50 占 퐉. The pore size and porosity present in the porous polymer substrate are not particularly limited, but the porosity is preferably in the range of 10 to 95% and the pore size (diameter) is preferably 0.1 to 50 탆. 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.

As described above, the thus-prepared separation membrane is interposed between the positive electrode and the negative electrode and exhibits a sufficient adhesion force, thereby preventing the separating membrane from being jammed, thereby preventing a short circuit between the positive electrode and the negative electrode.

Accordingly, the battery cell including the separation membrane according to the present invention is not particularly limited, and can be applied to all types and types of battery cells. However, when the separation membrane is further cut to form an atypical battery cell as described above, if the adhesive force between the electrode and the separator is low, the separator may be pushed during the separator cutting process, There is a problem that the short circuit between the positive electrode and the negative electrode becomes more serious due to the separation membrane swelling that occurs when the separator is formed. Therefore, the separator can be more preferably applied to the atypical battery cell.

Specifically, the battery cell according to the present invention may have an asymmetric structure with respect to a line passing through the center of the battery cell (the 'vertical center line') in the protruding direction of the electrode terminal, Or may have an asymmetrical structure with respect to a line passing through the center of the electrode (the 'transverse center line'), or a structure in which an opening is perforated therein. Of course, it may be asymmetric with respect to both the vertical centerline and the horizontal centerline.

One example according to an embodiment of the present invention of these structures is shown in Figs. 1 to 7 for convenience of understanding. However, it is needless to say that the present invention is not limited to the examples shown in the following drawings.

The battery cell may be a secondary battery, and more particularly, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery among the secondary batteries.

Other components of the battery cell according to the present invention will be described below.

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

The positive electrode active material is a lithium transition metal oxide. The lithium-transition metal oxide is a layered compound such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), which contains two or more transition metals and is substituted with, for example, one or more transition metals ; Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, Zn or Ga and Lim, 0.01≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0.4 Mn 0.4 Co 0.2 O 2 , such as _{Li 1 + z Ni b Mn c} Co 1- (b + c + d _{) M d O (2-e} ) A e ( where, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2 , 0≤e≤0.2, b + c + d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl; lithium nickel cobalt manganese composite oxide; And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The conductive material is usually added in an amount of 1 to 50% 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 that 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 50 wt% 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 prepared by coating, drying and pressing the negative electrode active material on the negative electrode current collector, and may optionally further include a conductive material, a binder, a filler, and the like as described above.

Examples of the negative electrode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene and activated carbon; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti which can be alloyed with lithium and compounds containing these elements; Complexes of metals and their compounds and carbon and graphite materials; Lithium-containing nitrides, and the like. Among them, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon based active material is more preferable, and these may be used singly or in combination of two or more.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

Meanwhile, the battery case in which the electrode assembly including the positive electrode, the negative electrode, and the separator is embedded includes an outer coating layer made of a weatherproof polymer, an inner sealant layer made of a heat-sealable polymer, and an inner sealant layer interposed between the outer coat layer and the inner sealant layer. The battery case may be a pouch type battery case made of an aluminum laminate sheet having a barrier layer made of Al.

The battery cell according to the present invention further includes a lithium salt-containing non-aqueous electrolyte in the battery case in addition to the electrode assembly. Specifically, the battery cell according to the present invention has a structure in which the electrode assembly is impregnated with a lithium salt-containing nonaqueous electrolyte.

The lithium salt-containing nonaqueous electrolyte is composed of a nonaqueous electrolyte and lithium. Nonaqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used as the nonaqueous electrolyte, but the present invention is not limited thereto.

Examples of the non-aqueous organic solvent 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, A polymer containing an ionic dissociation group and the like may 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 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In a preferred _{embodiment, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

The present invention also provides a battery module including the battery cell as a unit cell, a battery pack including the battery module, and a device including the battery pack.

Specific examples of the device include a mobile phone, a portable computer, a smart phone, a tablet PC, a smart pad, a netbook, a wearable electronic device, a LEV (Light Electronic Vehicle), an electric vehicle (EV), a hybrid electric vehicle An electric vehicle including a vehicle, a HEV, a plug-in hybrid electric vehicle (PHEV), and the like, but the present invention is not limited thereto.

The structure of the battery module and the battery pack, the method of manufacturing the same, the structure of the device, and the manufacturing method thereof are well known in the art, so a detailed description thereof will be omitted herein.

The battery cell according to the present invention comprises inorganic particles including a mixture of a metal oxide and a metal hydroxide, a PVdF-HFP polymer binder ('P _{HFP high} ') having a high hexafluoropropylene (HFP) content, Wherein the organic or inorganic porous coating layer comprising a mixture of a PVdF-HFP polymer binder ('P _{HFP low} ') is formed on at least one surface of the porous polymer substrate, It is possible to exhibit adhesion with an excellent electrode even if it is coated with a thin thickness and it is possible to effectively prevent a short circuit between the electrodes due to charging and discharging as well as to prevent a heat shrinkage ratio of the separating film, So that high capacity and high density battery characteristics and cell safety can be secured.

Further, when the separator has a sufficient adhesion with the electrodes, the separator is cut during the production of the atypical battery cell in which the shape of the electrode assembly itself is changed according to the shape of the device, It is possible to more precisely cut and prevent the short circuit between the electrodes caused by the jamming phenomenon, thereby further improving the safety of the battery cell.

1 is a graph showing the relationship between a line passing through the center of the battery cell in the protruding direction of the electrode terminal and a line passing through the center of the battery cell in the direction perpendicular to the protruding direction of the electrode terminal Is an example of an unshaped battery cell having an asymmetric structure;
2 is an example of an unshaped battery cell having an asymmetric structure with respect to a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal (the 'transverse center line'), and cutting the separator of the lower- A schematic diagram including a shape;
3 is an example of an unshaped battery cell having an asymmetric structure with respect to a line passing through the center of the battery cell in the protruding direction of the electrode terminal ('vertical center line');
4 is another example of an unshaped battery cell having an asymmetric structure with respect to a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal ('transverse center line');
5 is another example of an unshaped battery cell having an asymmetric structure with respect to a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal ('transverse center line');
6 is a graph showing a relationship between a line passing through the center of the battery cell in the protruding direction of the electrode terminal and a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal This is another example of an atypical battery cell having an asymmetric structure.
7 is a graph showing the relationship between a line passing through the center of the battery cell in the protruding direction of the electrode terminal and a line passing through the center of the battery cell in the direction perpendicular to the protruding direction of the electrode terminal This is another example of an atypical battery cell having an asymmetric structure.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

&Lt; Preparation Example 1 &

A PVdF-HFP polymer binder ("HFP18") containing HFP in an amount of 18% by weight and a PVdF-HFP polymer binder ("HFP5") containing HFP in an amount of 5% by weight were prepared These were added to acetone, respectively, and dissolved at 50 DEG C for about 12 hours to prepare a polymeric binder solution. As the inorganic particles, Al ₂ O ₃ powder and AlOOH powder were mixed at a molar ratio of 1: 0.1 and added to the polymer binder solution prepared so as to have a ratio of polymer binder / total inorganic particles = 10/90 by weight, and cyanylethyl polyvinyl alcohol Was added in an amount of 2% by weight of the polymer binder solution, and the inorganic particles were disrupted and dispersed by a ball mill method for 12 hours to prepare a slurry for an organic porous coating layer.

A slurry for an organic / inorganic porous coating layer was coated on both sides of the porous film by a dip coating method in an amount of 2.5 占 퐉 on a polyolefin porous film having a thickness of 9 占 퐉, followed by drying in an oven at 70 占 폚.

&Lt; Example 1 >

90 parts by weight of LiCoO ₂ as a positive electrode active material, 5 parts by weight of acetylene black as a conductive agent and 5 parts by weight of PVDF as a binder were mixed and added to NMP (Nmethyl-2-pyrrolidone) to prepare a positive electrode slurry, And dried to prepare a positive electrode.

95 parts by weight of Graphite as a negative active material and 5 parts by weight of SBR as a binder were added to distilled water to prepare an anode slurry, which was then coated on a copper (Cu) current collector and dried to prepare a negative electrode.

After dissolving LiPF ₆ in a nonaqueous solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1: 2 to a concentration of 1 M, 5 parts by weight of trimethylolpropane triacrylate as polymerizable monomer 0.15 part by weight of benzoyl peroxide (BPO) as an initiator was added to prepare a composition for an electrolyte.

Separator / anode / separator / separator / anode / separator / cathode structure by sandwiching the separator prepared in Preparation Example 1 between a plurality of anodes and cathodes to manufacture an electrode assembly by lamination, The composition was inoculated, vacuum packed and left at room temperature for 15 hours. Thereafter, the cell was polymerized at 80 DEG C for 4 hours to prepare a battery cell.

&Lt; Example 2 >

A separator was prepared in the same manner as in Preparation Example 1, except that HFP18 and HFP5 were prepared so as to have a weight ratio of 0.5: 7.0, and a battery cell was prepared in the same manner as in Example 1 except that the separator was used.

&Lt; Example 3 >

A separator was prepared in the same manner as in Preparation Example 1, except that HFP18 and HFP5 were prepared so as to have a weight ratio of 2.0: 6.0, and a battery cell was prepared in the same manner as in Example 1 except that the separator was used.

&Lt; Comparative Example 1 &

A separator was prepared in the same manner as in Preparation Example 1, except that HFP18 and HFP5 were prepared so as to have a weight ratio of 0: 8.5, and a battery cell was prepared in the same manner as in Example 1 except that the separator was used.

&Lt; Comparative Example 2 &

A separator was prepared in the same manner as in Preparation Example 1 except that HFP18 and HFP5 were prepared so as to have a weight ratio of 8.5: 0, and a battery cell was prepared in the same manner as in Example 1, except that the separator was used.

&Lt; Comparative Example 3 &

A battery cell was prepared in the same manner as in Example 1 except that a polyolefin porous film having a thickness of 14 탆 was used as a separator.

<Experimental Example 1>

The thickness and adhesion of the separator obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were measured and are shown in Table 1 below. At this time, the unit cells of the anode / separator / cathode were manufactured and measured using a tensile strength meter.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polymer
bookbinder
Furtherance
(HFP18: HFP5) 1: 7.5 0.5: 7.0 2.0: 6.0 0: 8.5 8.5: 0 - Inorganic particle Al ₂ O ₃
+ ALOOH Al ₂ O ₃
+ ALOOH Al ₂ O ₃
+ ALOOH Al ₂ O ₃
+ ALOOH Al ₂ O ₃
+ ALOOH - Thickness (㎛) 14.0 14.0 14.0 14.0 14.0 14.0 Adhesion (gf / 25mm) 20 15 27 13 5 0

Referring to Table 1, P _HFP the more _{high-containing} less appears to be a weak adhesive force of the separation membrane, P _{HFP high} and / or P _{HFP low} compared to Example 1 and the separation membrane of Comparative Example 2 has a separator which contains all so is not at all contained And it was found that it had weak adhesive force.

<Experimental Example 2>

In order to observe the extent of the punching at the time of cutting the separator, the process of cutting the separator of the lower edge portions according to the shape of the electrode in the battery cells of Example 1 and Comparative Examples 1, 2 and 3 as shown in FIG. 2 was performed. The results are shown in Table 2 below. The defect rate was measured for ten battery cells and the presence or absence of a part where there was a possibility of a short circuit due to the separation membrane between the anode and the cathode due to the swelling of the separator was measured.

Bad number Example 1 0 Comparative Example 1 2 Comparative Example 2 3 Comparative Example 3 8

Referring to Table 2, the defective rate of the battery cell of Example 1 was 0%, while the defective rate of about 10% to 30% occurred in the battery cells of Comparative Examples 1 and 2, and about 80% Defect rate occurred. This is because the separator adhesion of Comparative Examples 1, 2 and 3 was weak and the adhesion to the electrode was not good.

Claims (23)

An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
Wherein the separation membrane comprises a porous polymer base material and an organic or inorganic porous coating layer formed on at least one side of the porous polymer base material,
The organic or inorganic porous coating layer comprises inorganic particles including a mixture of a metal oxide and a metal hydroxide, a PVdF-HFP polymer binder ('P _{HFP high} ') having a high hexafluoropropylene (HFP) content, and a PVdF -HFP polymer binder ('P _{HFP low} '),
Wherein the adhesive force between the separator and the anode or the cathode is 15 gf / 25 mm or more. The battery cell of claim 1, wherein the P _{HFP high} comprises 8 to 20 wt% HFP on a weight basis. The battery cell of claim 1, wherein the P _{HFP low} comprises 3 to 15 wt% HFP on a weight basis. The battery cell according to claim 1, wherein the HFP content difference between the P _{HFP high} and the P _{HFP low} is 5 wt% or more based on the weight of each polymer binder. The battery cell according to claim 1, wherein the P _{HFP high} and P _{HFP low} are mixed at a weight ratio of 1: 3 to 1:20. The battery cell according to claim 1, wherein the metal oxide and the metal hydroxide include at least one metal. The battery according to claim 6, wherein the metal is at least one selected from the group consisting of Al, Ti, Sn, Ni, Mg, Ce, Sn, Sr, Pb, Si, Zn, Zr Ca, Cell. The battery cell according to claim 6, wherein the metal oxide is Al ₂ O ₃ and the metal hydroxide is AlOOH. The battery cell according to claim 1, wherein the inorganic particles are contained in an amount of 50% by weight to 95% by weight based on the total weight of the organic porous coating layer. The battery cell according to claim 1, wherein the organic or inorganic porous coating layer is formed to a thickness of 0.5 micrometers to 5 micrometers based on a cross section of the porous polymer substrate. The battery cell according to claim 1, wherein the porous polymer substrate is a nonwoven fabric made of a polyolefin porous film or a polyethylene terephthalate fiber. The battery cell according to claim 1, wherein the adhesive force between the separator and the anode or the cathode is 15 gf / 25 mm to 30 gf / 25 mm. The battery cell according to claim 1, wherein the battery cell has an asymmetric structure with respect to a line passing through the center of the battery cell in the projecting direction of the electrode terminal ('vertical center line'). The battery cell according to claim 1, wherein the battery cell has an asymmetric structure with respect to a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal ('transverse center line'). The battery cell according to claim 1, wherein the battery cell has a structure in which an opening is formed in the battery cell. The battery cell according to claim 1, wherein the battery cell is a lithium secondary battery. A battery module comprising the battery cell according to claim 1 as a unit cell. A battery pack comprising the battery module according to claim 17. A device comprising a battery pack according to claim 18. 20. The device of claim 19, wherein the device is a mobile phone, a portable computer, a smart phone, a tablet PC, a smart pad, a netbook, a wearable electronic device, a LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, , And a power storage device. A battery case; And an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, the electrode assembly being embedded in the battery case,
Wherein the separation membrane comprises a porous polymer base material and an organic or inorganic porous coating layer formed on at least one side of the porous polymer base material,
The battery cell may have an asymmetric structure with respect to a line passing through the center of the battery cell in the protruding direction of the electrode terminal (the 'vertical center line'), or may have a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal And &quot; transverse center line &quot;). The battery cell according to claim 21, wherein the battery cell has an asymmetric structure with respect to a line passing through the center of the battery cell in the projecting direction of the electrode terminal ('vertical center line'). The battery cell according to claim 21, wherein the battery cell has an asymmetric structure with respect to a line passing through the center of the battery cell in a direction perpendicular to the protruding direction of the electrode terminal ('transverse center line').

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