KR20170043240A - Electrode Assembly Comprising Electrode Having High Loading Amount of Active Material at Middle of Current Collector - Google Patents

Abstract

The present invention relates to an electrode assembly which comprises a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes. The positive and negative electrodes include active material coating parts on one or both sides of a plate shaped current collector, and electrode tabs, which are not coated by an electrode active material, are formed on one end of the current collector. An electrode tab of the positive electrode and an electrode tab of the negative electrode face each other and are formed on both ends of the electrode assembly. In the positive and negative electrodes, a loading amount of the active material coating parts decreased from the central portion of the current collector toward left and right longitudinal directions.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode assembly including an electrode having a high active material loading amount at a central portion of a current collector,

The present invention relates to an electrode assembly in which a positive electrode and a negative electrode each have a structure in which a loading amount of an active material coating portion decreases in a longitudinal direction of both sides from a central portion of the current collector.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy or clean energy is increasing. As a part of this, the most active field of research is electric power generation and storage.

At present, a typical example of an electrochemical device utilizing such electrochemical energy is a secondary battery, and the use area thereof is gradually increasing.

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

The electrode assembly incorporated in the battery case is a charge / dischargeable power generating element formed of a laminate structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a jelly-roll type in which a separator is interposed between a positive electrode and a negative electrode coated with an active material, Sized positive and negative electrodes are stacked in a stacked state in a state in which a separator is interposed therebetween.

A full cell or anode / separator / cathode / separator / separator / separator / cathode assembly having a positive electrode / separator / negative electrode structure with a constant unit size, which is a progressive structure of a jelly- A stack / folding type electrode assembly having a structure in which a bicell having a cathode structure is folded by using a continuous long separator film has been developed.

Further, in order to improve the processability of the conventional stacked electrode assembly and meet the demands of various types of secondary batteries, a lamination / stacked electrode structure in which unit cells alternately laminated and laminated are laminated Assemblies have also been developed.

Such secondary batteries are attracting attention as power sources requiring high output such as electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-In HEVs). In response to this tendency, It is expanding.

Particularly, in the case of a middle- or large-sized secondary battery requiring high output, a rectangular plate-shaped battery is mainly used in consideration of the internal space of a device in which the battery is mounted. At this time, the loading amount of the active material is increased to increase the thickness, Larger plate-shaped battery cells are mainly used.

1 is a schematic diagram of a conventional plate-shaped electrode assembly 100 according to the prior art.

1, the electrode tabs 113 of the anode 110 and the electrode tabs 123 of the cathode 120 are formed at both ends of the electrode assembly 100 so as to face each other. The anode 110 includes a cathode active material coating portion 112 on both sides of the plate-like current collector 111 and an electrode tab 113 having no active material coated on one end of the current collector 111 is formed. In addition, the loading amount of the positive electrode active material is equally coated at an arbitrary position of the active material coating portion 112. Similarly, the cathode 120 includes an anode active material coating portion 122 on both sides of the plate-like current collector 121, and an electrode tab 123 not coated with an active material is formed at one end of the current collector 121 . In addition, the loading amount of the negative electrode active material is equally coated at an arbitrary position of the active material coating portion 122.

Generally, when such a plate-shaped battery cell is charged and discharged, a current is actively moved in a region of the electrode tab having a low resistance, so that the electrode active material in the vicinity of the electrode tab is expected to be used more than the electrode active material located far away from the electrode tab It has been confirmed through experimentation of the present invention that the electrode active material is actually used more in the longitudinal center portion of the current collector (for reference, the method and results of this experiment are described later).

The biased use of such an electrode active material causes local early degeneration of the electrode, which ultimately shortens the life of the battery cell and hinders stable output. As battery cells become larger and energy density increases, this is becoming a more serious problem.

Therefore, a need exists for a technique capable of overcoming 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 have made various experiments and intensive studies and have developed an electrode assembly having a structure in which the amount of loading of the active material coating portion decreases in the lengthwise direction on both sides from the central portion of the current collector, It has been confirmed that a desired effect can be achieved when used, and the present invention has been accomplished.

Accordingly, the present invention provides an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode and the negative electrode include an active material coating portion on one surface or both surfaces of the plate- Wherein the positive electrode tab and the negative electrode tab are formed at opposite ends of the electrode assembly so as to face each other and the positive electrode and the negative electrode are formed on both sides of the active material coating portion And the amount of loading is reduced in the longitudinal direction on both sides from the central portion of the current collector.

That is, the electrode assembly according to the present invention has a structure in which the loading amount of the active material coating portion decreases in the longitudinal direction on both sides from the central portion of the current collector, thereby preventing the electrode from being biased and minimizing the problem of locally degenerating the electrode can do.

The loading amount of the active material can be variously adjusted depending on the thickness and density of the coating. In one specific example, the density of the coating at any position of the active material coating portion is the same, and the coating thickness may be formed differently depending on the loading amount. In such a structure, the coating thickness may be formed so as to be the same in the width direction of the current collector at an arbitrary position with respect to the center portion of the current collector, and to decrease in both the longitudinal direction.

At this time, the thickness of the coating at the center of the current collector may be determined in consideration of the output of the battery, the resistance generated by the current flow at the central portion of the current collector during operation of the battery cell, the volume of the battery, May range from 101% to 250%, in particular from 110% to 150%, relative to the coating thickness at both end portions.

If the thickness is less than 101% and the thickness is less than 101%, the electrode active material is more likely to be used at the center of the current collector than the electrode active material at a distance from the center of the current collector, If it exceeds 250%, the shape of the electrode assembly due to an excessive thickness difference may be asymmetric and the manufacturing process may not be easy, which is not preferable.

In another specific example, the coating thickness may be the same at any position of the active material coating portion, may be formed to have a different coating density depending on the loading amount, and specifically, the coating density may be formed so as to decrease in both longitudinal directions.

At this time, the coating density at the central portion of the current collector may be determined in consideration of the output of the battery, the resistance generated by the flow of electrons at the central portion of the current collector during operation of the battery cell, the volume of the battery, May range from 101% to 300%, in particular from 110% to 250%, relative to the coating density of the region.

If the density is less than 101%, the electrode active material is more likely to be used at the center of the current collector than in the electrode active material at a distance from the center of the current collector during operation of the battery cell, leading to premature degradation of the electrode , And when it is more than 250%, there is a risk of ignition due to excessive resistance due to excessive flow of electrons generated in the center portion of the current collector due to an excessive density difference during operation of the battery cell, Process and cost are incurred.

In another specific example, the electrode assembly may be formed with the same amount of loading at the same distance from the center portion with respect to the central portion of the current collector. In one example, the coating thickness or coating density according to the amount of loading may be increased or decreased by forming a radial contour structure on the basis of the central portion. As described above, in the case of a high-output battery, the specification of the plate-shaped battery is enlarged, so that the partial early degradation phenomenon due to the biased use of the electrode generated in the longitudinal direction of the plate-shaped battery occurs in the width direction. , The coating thickness or coating density may change to a radial contour structure based on the central portion of the current collector.

In another specific example of the electrode assembly according to the present invention, the positive electrode and the negative electrode each have a structure in which the loading amount of the active material coating portion increases toward the center portion of the current collector, and the loading amount of the negative electrode active material coating portion at any position is, It may be formed to be equal to or larger than the loading amount of the coating portion. With this configuration, the possibility of short circuit due to lithium precipitation in the cathode can be minimized.

At this time, the loading amount of the negative electrode active material coating portion at the arbitrary position may be determined in consideration of the output of the battery, the resistance generated by the current flow at the central portion of the current collector when the battery cell is operated, And may range from 100% to 120% of the cathode active material coating portion.

Other components included in the other battery cells of the present invention will be described below.

The positive electrode is prepared by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The collector for a positive electrode generally has a thickness of 3 to 500 mu m. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, The surface of the steel may be surface treated with carbon, nickel, titanium, silver, or the like. 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 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 = 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; 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); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _2-x O ₄ (where 0? _X <1); 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 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.

The collector for a negative electrode is generally made to have a thickness of 3 to 500 mu m. Such a current collector for a negative electrode is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, 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.

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 < x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

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

The electrolyte solution contained in the battery case together with the electrode assembly may be a lithium salt-containing nonaqueous electrolyte solution comprising a nonaqueous electrolyte solution and a lithium salt. The nonaqueous electrolyte solution may be a nonaqueous organic solvent, an organic solid electrolyte, But are not limited to these.

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 3SO2) 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 may contain at least one selected from the group consisting of 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 may be added have. 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.

For example, a lithium salt such as LiPF ₆ , LiClO ₄ , LiBF ₄ , or LiN (SO ₂ CF ₃ ) ₂ is mixed with a cyclic carbonate of EC or PC as a high-dielectric solvent and a linear carbonate such as DEC, DMC or EMC To the mixed solvent to prepare an electrolytic solution.

The present invention also provides a battery cell in which an electrode assembly is embedded in a battery case together with an electrolyte solution.

In one specific example, the battery case may be a cylindrical case, the cathode terminal may be directly connected to the cap assembly mounted at the open upper end of the cylindrical case, and the cathode terminal may be directly connected to the inner surface of the cylindrical case.

In another specific example, the battery case may be a rectangular case, and the positive electrode terminal and the negative electrode terminal may be directly connected to the respective terminal connecting portions of the top plate mounted on the open upper end of the cylindrical case.

In some cases, the battery case may be a pouch-type case, and the positive electrode terminal and the negative electrode terminal may be directly connected to the respective terminal connection portions of the protection circuit member mounted on the outside of the pouch-shaped case. In particular, the pouch-shaped battery case may be formed of a laminate sheet including a metal layer and a resin layer, and more particularly, an aluminum laminate sheet whose metal layer is Al.

The present invention also provides a device using a battery pack including the battery cell as a power source.

Specific examples of such a device include a mobile device, a wearable device, a power tool powered by an electric motor, and the like. An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; And may be an energy storage system (Energy Storage System).

The manufacturing method of the device is well known in the art, and a description thereof will be omitted herein.

INDUSTRIAL APPLICABILITY As described above, the electrode assembly according to the present invention can solve the unbalanced use of the active material in the same electrode to prevent the electrode from being used in a deflected manner, thereby realizing stable output and prolonging the life of the battery. I could

1 is a schematic diagram of an electrode assembly according to the prior art;
2 is a schematic diagram of an electrode assembly according to one embodiment of the present invention;
3 is a schematic view of an electrode assembly according to another embodiment of the present invention;
4 is a schematic diagram of an electrode assembly according to another embodiment of the present invention;
5 is a schematic diagram of a cathode according to another embodiment of the present invention;
FIG. 6 is a plan view and a cross-sectional view of a battery cell in which a third electrode is provided to measure the internal resistance of the negative electrode of the electrode assembly of FIG. 1;
FIG. 7 is a graph showing changes in internal resistance according to charge measured at the cathode of FIG. 6; FIG.

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

2 is a schematic diagram of an electrode assembly 200 according to one embodiment of the present invention

Referring to FIG. 2, the electrode tab 213 of the anode 210 and the electrode tab 223 of the cathode 220 are formed at opposite end portions of the electrode assembly 200 facing each other. The anode 210 includes a cathode active material coating portion 212 on both sides of the plate-like current collector 211 and an electrode tab 213 having no active material coated on one end of the current collector 211. The coating density is the same at any position of the active material coating portion 212 and the coating thickness is the same as the thickness of the active material coating portion 212 in the width direction of the current collector 211 And the thickness of the coating decreases in the longitudinal direction of both sides at the central portion of the current collector 211. In this case, Accordingly, the amount of loading of the cathode active material coating portion 212 decreases in the longitudinal direction of both sides at the central portion of the current collector 211. [

Similarly, the cathode 220 includes an anode active material coating portion 222 on both sides of the plate-like current collector 221, and an electrode tab 223 having no active material coated on one end of the current collector 221 is formed . The coating density is the same in any position of the active material coating part 222 and the coating thickness is the same in the width direction of the current collector 221 at an arbitrary position with respect to the central part of the current collector 221, The thickness decreases in the longitudinal direction on both sides from the central portion of the current collector 221. [ Accordingly, the loading amount of the negative electrode active material coating portion 222 decreases in both longitudinal directions from the central portion of the collector 221 as a whole.

In addition, the thickness of the coating at the central portions of the current collectors 211 and 221 is in the range of 101% to 250% with respect to the thickness of the coating at both ends.

3 is a schematic diagram of an electrode assembly 300 according to another embodiment of the present invention.

3, the electrode tabs 313 of the anode 310 and the electrode tabs 323 of the cathode 320 are formed at opposite ends of the electrode assembly 300 facing each other. The anode 310 includes a cathode active material coating portion 312 on both sides of the plate-like current collector 311 and an electrode tab 313 having no active material coated on one end of the current collector 311 is formed. The coating thickness is the same at any position of the active material coating portion 312 and the coating density is the same in the width direction of the current collector 311 at an arbitrary position with respect to the center portion of the current collector 311, And decreases in the longitudinal direction on both sides at the central portion of the whole body 311. Accordingly, the loading amount of the cathode active material coating portion 312 is reduced in the longitudinal direction of both sides at the central portion of the current collector 311.

Similarly, the cathode 320 includes an anode active material coating portion 322 on both sides of the plate-like current collector 321, and an electrode tab 323 having no active material coated on one end of the current collector 321 is formed . The coating thickness is the same in any position of the active material coating portion 322 and the coating density is the same in the width direction of the current collector 321 at an arbitrary position with respect to the center portion of the current collector 321, And decreases in the longitudinal direction on both sides at the central portion of the whole body 321. Therefore, the loading amount of the negative electrode active material coating portion 322 decreases in the longitudinal direction on both sides at the center portion of the current collector 321.

In addition, the density of the coating in the central portion of the current collectors 311 and 321 is in the range of 101% to 300% with respect to the density of the coating at both end portions.

4 is a schematic view of an electrode assembly according to another embodiment of the present invention.

4, the electrode tabs 413 of the anode 410 and the electrode tabs 423 of the cathode 420 are formed at opposite ends of the electrode assembly 400 facing each other. The anode 410 includes a cathode active material coating portion 412 on both sides of the plate-like current collector 411 and an electrode tab 413 having no active material coated on one end of the current collector 411 is formed. The coating density is the same at any position of the active material coating portion 412 and the coating thickness is the same in the width direction of the current collector 411 at any position with respect to the center portion of the current collector 411, The coating thickness decreases in the longitudinal direction on both sides from the central portion of the current collector 411. [ Accordingly, the amount of loading of the cathode active material coating portion 412 decreases in the longitudinal direction of both sides at the central portion of the current collector 411. [

Likewise, the cathode 420 includes an anode active material coating portion 422 on both sides of the plate-like current collector 421, and an electrode tab 423 having no active material coated on one end of the current collector 421 . The coating density is the same in any position of the anode active material coating portion 422 and the coating thickness is the same in the width direction of the current collector 421 at an arbitrary position with respect to the center portion of the current collector 421, The coating thickness decreases in the longitudinal direction on both sides at the central portion of the current collector 421. [ Accordingly, the loading amount of the anode active material coating portion 422 is reduced in the longitudinal direction of both sides of the current collector 421 at the central portion thereof.

The thickness of the coating at the central portions of the current collectors 411 and 421 is in the range of 101% to 250% with respect to the coating thickness at the both end portions, and the loading amount of the negative electrode active material coating portion 422 at any position is, Is larger than the loading amount of the active material coating portion 412.

As described above, the configuration in which the loading amount of the negative electrode active material coating portion at an arbitrary position is equal to or larger than the loading amount of the positive electrode active material coating portion is also applicable to the embodiment shown in FIG.

5 is a schematic diagram of a cathode according to another embodiment of the present invention.

5, the anode 510 includes a cathode active material coating portion 512 on both surfaces of a plate-shaped current collector, and an electrode tab 513 having no active material coated on one end of the current collector is formed. The coating amount or coating density according to the amount of loading is the same as that of the radial contour lines 520, 521, 522, 523 , 524), and it increases to a gentle slope toward the center of the current collector. Also, the loading amount of the current collector central portion corresponds to the range of 101% to 250% with respect to the loading amount of the outermost contour 520.

The structure in which the coating thickness or coating density according to the loading amount forms a radial contour structure with respect to the central portion of the current collector and increases to a gentle slope toward the central portion of the current collector is also applied to the cathode (not shown).

FIG. 6 is a plan view and a cross-sectional view of a battery cell in which a third electrode is provided to measure the internal resistance of the negative electrode of the electrode assembly of FIG. 1, and FIG. 7 is a graph showing internal resistance according to the charge measured at the negative electrode of FIG. 6 .

6 and 7, the electrode leads of the positive electrode and the electrode leads of the negative electrode are formed on both side ends of the electrode assembly facing each other. The positive electrode includes a cathode active material coating portion on both sides of the plate-like current collector, and an electrode tab is formed on one end of the current collector, the electrode tab not coated with an active material. In addition, the loading amount of the positive electrode active material is equally coated at an arbitrary position of the active material coating portion. Similarly, the negative electrode includes a negative electrode active material coating portion on both sides of the plate-like current collector, and an electrode tab is formed on one end of the current collector without coating the active material. In addition, the loading amount of the negative electrode active material is equally coated at an arbitrary position of the active material coating portion. Here, W represents the cross-sectional shape of both side sealing portions of the battery cell in which the electrode lead is not formed. In order to measure the internal resistance of the cathode according to the position, the third electrode was provided at each of the anode region, the cathode region, and the center portion in the longitudinal direction, and the internal resistance was measured according to the charging degree.

The graph of FIG. 7 shows the change of the internal resistance according to the positions of the cathodes according to the degree of filling. As a result of the test, it was confirmed that the internal resistance was lowest at the center portion in the longitudinal direction of the negative electrode when the battery cell was charged.

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

Claims (17)

An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,
The positive electrode and the negative electrode include an active material coated portion on one side or both sides of the plate-shaped current collector, and an electrode tab is formed on one end of the current collector without coating the electrode active material;
The electrode tabs of the positive electrode and the electrode tabs of the negative electrode are formed at both side ends of the electrode assembly facing each other;
Wherein the positive electrode and the negative electrode have a structure in which a loading amount of the active material coating portion decreases in the longitudinal direction on both sides from the central portion of the current collector. The electrode assembly according to claim 1, wherein the coating density is the same at any position of the active material coating portion, and the coating thickness is different according to the loading amount. The electrode assembly according to claim 2, wherein the coating thickness is the same in a width direction of the current collector at an arbitrary position with respect to a center portion of the current collector. 3. The electrode assembly of claim 2, wherein the thickness of the coating decreases in the longitudinal direction on both sides of the central portion of the current collector. 5. The electrode assembly according to claim 4, wherein the thickness of the coating at the central portion of the current collector is in the range of 101% to 250% with respect to the coating thickness of both side end portions. 6. The electrode assembly according to claim 5, wherein the thickness of the coating at the central portion of the current collector ranges from 110% to 150% with respect to the coating thickness of both end portions. The electrode assembly according to claim 1, wherein the coating thickness is the same at an arbitrary position of the active material coating portion, and the coating density is different depending on the loading amount. 8. The electrode assembly of claim 7, wherein the coating density of the active material coating decreases in both longitudinal directions. 9. The electrode assembly of claim 8, wherein the coating density in the central region is in the range of about 101% to about 300% of the coating density at both ends. 10. The electrode assembly of claim 9, wherein the coating density at the center portion is in the range of 110% to 250% relative to the coating density at both end portions. The electrode assembly according to claim 1, wherein a loading amount is the same at the same distance from the central portion with respect to a center portion of the current collector. 12. The electrode assembly of claim 11, wherein the coating thickness or coating density according to the amount of loading represents a radial contour structure with respect to a central portion. [2] The method of claim 1, wherein the positive electrode and the negative electrode each have a structure in which the loading amount of the active material coating portion increases toward the central portion;
Wherein a loading amount of the negative electrode active material coating portion at an arbitrary position is equal to or greater than a loading amount of the positive electrode active material coating portion. 14. The electrode assembly according to claim 13, wherein the loading amount of the negative electrode active material coating portion at any position is in a range of 100% to 120% of the loading amount of the positive electrode active material coating portion. The battery cell according to claim 1 or 13, wherein the electrode assembly is embedded in the battery case together with the electrolyte solution. A battery pack comprising a battery cell according to claim 15. 17. A device comprising the battery pack according to claim 16 as a power source.

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