KR20210038257A - Jelly-Roll Type Electrode Assembly Comprising Positive Electrode Having Pattern-Coated Part and Secondary Battery comprising the same - Google Patents

Abstract

Provided is a jelly-roll type electrode assembly wound with a separator interposed between a positive electrode and a negative electrode. Provided are an electrode assembly and a secondary battery including the same, wherein the positive electrode includes a core unit and an outer unit. The core unit includes a first positive electrode current collector, a first positive electrode mixture layer positioned on the first positive electrode current collector, and a second positive electrode mixture layer positioned on the first positive electrode mixture layer. The outer unit includes a second positive electrode current collector, and a third positive electrode mixture layer positioned on the second positive electrode current collector. The second positive electrode mixture layer has an applied unit and an uncoated unit.

Description

Jelly-Roll Type Electrode Assembly Comprising Positive Electrode Having Pattern-Coated Part and Secondary Battery comprising the same

The present invention relates to a jelly-roll type electrode assembly including a positive electrode coated with some pattern, and a secondary battery including the same.

In recent years, as technology development and demand for mobile devices increase, the demand for rechargeable and dischargeable secondary batteries as an energy source is rapidly increasing, and accordingly, many studies on secondary batteries that can meet various demands have been conducted. In addition, the secondary battery is an electric vehicle (EV), hybrid electric vehicle (HEV), and plug-in hybrid electric vehicle that has been proposed as a solution to air pollution such as gasoline vehicles and diesel vehicles that use fossil fuels. It is also attracting attention as a power source such as (Plug-in HEV).

Therefore, electric vehicles (EV) that can be operated with only secondary batteries, hybrid electric vehicles (HEVs) that use secondary batteries and existing engines together have been developed, and some are commercially available. Secondary batteries as power sources such as EVs and HEVs are mainly nickel hydride metal (Ni-MH) secondary batteries, but in recent years, studies using lithium secondary batteries with high energy density, high discharge voltage, and output stability are actively progressing. And some have been commercialized.

Depending on the shape of the battery case, the lithium secondary battery is a cylindrical battery and a prismatic battery in which an electrode assembly is embedded in a cylindrical or rectangular metal can, and a pouch-type battery in which the electrode assembly is embedded in a pouch-shaped case of an aluminum laminate sheet. Classified.

In addition, the electrode assembly built into the battery case has a structure in which a positive electrode, a negative electrode, and a separator are interposed between the positive electrode and the negative electrode, and is a power generating device capable of charging and discharging. A jelly-roll type wound interposed, a stack type in which a plurality of positive and negative electrodes of a predetermined size are sequentially stacked in a state interposed on a separator, and a full cell consisting of electrodes of different polarities on both sides (for example, a positive electrode-separator- A unit cell such as a cathode) or a bi-cell (eg, anode-separator-cathode-separator-anode) composed of electrodes of different polarities on both sides is placed on a long sheet-shaped separator and wound into a stack-folding type. Classified.

Among them, the jelly-roll type electrode assembly (hereinafter referred to as'jelly-roll') is easy to manufacture and has high energy per weight, and the cylindrical or prismatic battery including it has high safety and no change in volume, so it is a power source. Along with the expansion of the market for EVs and HEVs, the demand for prismatic or cylindrical secondary batteries is increasing rapidly.

Meanwhile, the positive electrode and the negative electrode are generally manufactured by coating an electrode mixture including an active material on both surfaces of each current collector, and various materials are used as the active material.

Among these, as a negative electrode active material, a material containing graphite is widely used. When a material containing graphite releases lithium, the average potential is about 0.2V (based on Li / Li+), and the potential changes relatively flatly during discharge. For this reason, there is an advantage in that the voltage of the battery is high and constant. However, while the electrical capacity per unit mass of the graphite material is as small as 372 mAh/g, the current capacity of the graphite material is improved close to the above theoretical capacity, so that further increase in capacity is difficult.

Accordingly, in order to further increase the capacity of the lithium secondary battery, various negative active materials have been studied. As a high-capacity negative electrode active material, a material that forms a lithium-intermetallic compound, such as silicon or tin, is expected as a promising negative electrode active material. In particular, silicon is an alloy-type negative electrode active material having a theoretical capacity (4,200 mAh/g) that is about 10 times higher than that of graphite, and is in the spotlight as a negative electrode active material for lithium secondary batteries today.

However, a silicon-based material containing silicon has a large volume change during charging and discharging, e.g., ~400% for Si and _{~200% for SiO x} , so in the case of a rectangular or cylindrical battery with a volume limitation, the built-in When the electrode assembly is pressed by the case, the electrolyte solution impregnated in the electrode assembly collects in the upper and lower portions of the battery, and thus, there is a problem that lithium plating precipitation and deterioration in life characteristics occur.

Accordingly, there is a high need for a jelly-roll type electrode assembly having improved safety and lifespan characteristics by solving the above problems.

An object of the present invention is to solve the problems of the prior art and technical problems that have been requested from the past.

Specifically, the object of the present invention is to prevent the electrolytic solution from being pulled by multilayer coating and pattern coating of the core part on the anode of the jelly-roll type electrode assembly, so that the electrolyte can be stored even when the electrode assembly is compressed during volume expansion of the electrode assembly. By doing so, it is to provide an electrode assembly capable of improving the safety and life characteristics of a secondary battery including the same.

According to the present invention for achieving this object,

In the jelly-roll type electrode assembly wound with a separator interposed between an anode and a cathode,

The anode includes a core portion and an outer portion,

The core portion includes a first positive electrode current collector, a first positive electrode mixture layer disposed on the first positive electrode current collector, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer,

The outer portion includes a second positive electrode current collector and a third positive electrode mixture layer positioned on the second positive electrode current collector,

The second positive electrode mixture layer is provided with an electrode assembly having an applied portion and an uncoated portion.

That is, the jelly-roll type electrode assembly according to the present invention creates a space in which the electrolyte solution can be stored in the core portion where the electrolyte solution is not well impregnated in the wound type jelly-roll type electrode assembly, thereby preventing the volume expansion of the electrode assembly. As a result, the electrolyte can be maintained in a form impregnated in the electrode even by compression, so that precipitation and a decrease in life due to the electrolytic solution can be prevented.

In addition, since the formation of the space by the pattern coating is performed only in the core part, the energy density per volume of the battery can be improved by not applying the pattern coating to the outer part with relatively excellent electrolyte impregnation, thereby minimizing damage in terms of capacity. I can make it.

In the present invention, the core portion and the outer portion have the terms defined in the shape of the wound electrode assembly, but are divided based on the length in the winding direction, and the boundary may be appropriately selected at a general level, but in detail In order to exert the above effect of the present invention, for example, the core part is within 50% of the total length from the time of winding to the end of winding of the electrode assembly, in detail, It may be within 30%, and may be in the range of 5% or more, specifically, 10% or more.

cathode

The electrode assembly according to the present invention is particularly effective when the volume change due to charging and discharging is large.

Further, in order to compensate for the capacity that decreases with the formation of the space, a material exhibiting a high capacity is desirable.

Accordingly, in the electrode assembly according to the present invention, the negative electrode may include a negative electrode current collector and a negative electrode mixture layer positioned on the negative electrode current collector, and the negative electrode mixture layer may include a Si-based material as a negative electrode active material. .

At this time, the negative electrode active material may include a Si-based material, 5% by weight or more based on the total weight of the negative electrode active material, specifically, may be included in 5% by weight to 30% by weight, in detail, 10% by weight It may be included in to 20% by weight.

At this time, the Si-based material is a Si/C composite, SiO _x (0<x<2), metal-doped SiO _x (0<x<2), SiO _x /C (0<x<2), pure Si It may be one or more selected from the group consisting of (pure Si) and Si alloys (Si-alloy).

The Si/C composite is, for example, a configuration in which a carbon material is coated on the particle surface by heat treatment (firing) in a state in which carbon is bonded to silicon or silicon oxide particles, or carbon is dispersed in an atomic state inside the silicon particles. The configuration may be the same as the configuration or the silicon/carbon composite of the applicant's PCT international application WO 2005/011030, and the configuration is not limited as long as the carbon and the silicon material form a composite.

The silicon oxide (SiO _x ) may be 0<x≦1, and includes a configuration in which surface treatment such as a carbon coating layer is performed on the surface of the silicon oxide.

SiO _x /C (0<x<2) includes a composite or coated composition of silicon oxide and carbon.

In addition, the metal-doped SiO _x (0<x<2) may have a configuration in which at least one metal selected from the group consisting of Li, Mg, Al, Ca, and Ti is doped.

When doped as described above, SiO _x irreversible in to reduce the SiO ₂ onto the material, or electrochemically inactive metal-silicate (metal-silicate) phase in the bar which was to improve the initial efficiency of the SiO _x material conversion, More preferable.

The metal oxide-coated SiO _x (0<x<2) may have, for example, Al ₂ O ₃ , or _{a configuration in which TiO 2} or the like is coated.

The Si alloy (Si-alloy) is an alloy in which Si is alloyed with one or more metals selected from the group consisting of Zn, Al, Mn, Ti, Fe, and Sn, and a solid solution thereof, an intermetallic compound, a eutectic alloy, etc. Although can be mentioned, it is not limited only to these.

In addition to the Si-based material, the negative electrode active material is composed of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjen black, super P, graphene, and fibrous carbon. At least one carbon-based material selected from the group, Si-based material, 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': Al, B, P, Si, elements of groups 1, 2 and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3; 1 Metal composite oxides such as ?z?8); Lithium metal; Lithium alloy; Tin-based alloys; 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 metal oxides such as _{Bi 2} O _5; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; It may further include lithium titanium oxide, but is not limited thereto.

Meanwhile, the negative electrode mixture layer may further include a conductive material and a binder together with the negative electrode active material, and optionally a filler may be further included.

The conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery as a conventionally known conductive material. For example, carbon black, acetylene black, Ketjen black, channel black, furnace black, Carbon black such as lamp black and summer black; Conductive fibers such as carbon fibers and metal fibers; 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 may be used.

The binder is not limited as long as it is a component that aids in the bonding of the active material and the conductive material and bonding to the current collector, and for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, Hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber , May be each selected from a variety of copolymers.

At this time, the conductive material and the binder may be included in 0.1 to 30% by weight, specifically, 0.5 to 10% by weight, more specifically, 1 to 5% by weight, based on the total weight of the negative electrode mixture layer.

The filler is selectively used as a component that suppresses the expansion of the negative electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes to the battery, and examples thereof include olefin-based polymers such as polyethylene and polypropylene; A fibrous material such as glass fiber or carbon fiber may be used, and may be included in an amount of 1 to 5% by weight based on the total weight of the negative electrode mixture layer.

The negative electrode current collector is generally manufactured to a thickness of 3 to 200 μm, and is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel , Titanium, calcined carbon, surface-treated carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, it is possible to enhance the bonding strength of the negative electrode active material by forming fine irregularities on the surface thereof, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

anode

According to the present invention, the positive electrode is more effectively impregnated with the electrolytic solution to prevent the electrolytic solution inside the electrode assembly from being compressed to the outside of the electrode assembly by being compressed during battery charging and discharging, while impregnating the electrolytic solution inside the electrode assembly. It is manufactured in a form that forms a storage space.

Specifically, the core portion includes a first positive electrode current collector, a first positive electrode mixture layer disposed on the first positive electrode current collector, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer,

The outer portion includes a second positive electrode current collector and a third positive electrode mixture layer positioned on the second positive electrode current collector,

The second positive electrode mixture layer may have a coated portion and an uncoated portion.

By having an uncoated portion in which the positive electrode mixture layer is not formed in the core portion of the wound type jelly-roll type electrode assembly as described above, there is a difference in thickness from the applied portion, thereby providing a space for storing the electrolyte solution. As can be achieved, the effect according to the present invention can be obtained.

However, in the case of being entirely formed from the jelly-roll type electrode assembly, the electrolyte storage performance may be excellent, but the energy density of the battery decreases, thereby reducing the capacity, which is not preferable.

On the other hand, in the present invention, the terms of the first positive electrode mixture layer, the second positive electrode mixture layer, and the third positive electrode mixture layer are only terms for distinguishing regions having different shapes, and at the time of manufacture, they are integrally or separately. It can be formed as

Similarly, the first positive electrode current collector and the second positive electrode current collector of the core part are also terms used to distinguish between the core part and the outer part, and the first positive electrode current collector and the second positive electrode current collector may be formed integrally or separately. have.

For example, the first positive electrode mixture layer, the second positive electrode mixture layer, and the third positive electrode mixture layer may all be separately formed, and the thickness of each may be adjusted, so that the first positive electrode mixture layer and the second positive electrode mixture layer The combined thickness and the thickness of the third positive electrode mixture layer may be similarly formed.

As another example, on one positive electrode current collector, a first positive electrode slurry was first applied to the entire core portion and the outer portion to integrally form the first positive electrode mixture layer and the third positive electrode mixture layer. 1 It is possible to manufacture the positive electrode of the present invention by forming the second positive electrode slurry to include the coated portion and the uncoated portion only on the positive electrode mixture layer.

In this case, the thickness of the first positive electrode mixture layer may be smaller than the thickness of the third positive electrode mixture layer. In other words, when applying the first positive electrode slurry, the first positive electrode slurry is applied thicker to the outer part than the core part, and the combined thickness of the first positive electrode mixture layer and the second positive electrode mixture layer and the third positive electrode The thickness of the mixture layer can be similarly formed.

As another example, a first positive electrode slurry is first applied to one positive electrode current collector on the entire core portion and the outer portion to form a first positive electrode mixture layer and a 3-1 positive electrode mixture layer, and then again, the first positive electrode slurry is applied to the core portion. On the positive electrode mixture layer, a second positive electrode slurry is formed to include the coated part and the uncoated part, but the second positive electrode slurry is applied entirely on the 3-1 positive electrode mixture layer of the outer part, and the second positive electrode mixture layer, the 3-2 positive electrode An anode can be manufactured by forming a mixture layer. In this case, the third positive electrode mixture layer refers to the entire 3-1 positive electrode mixture layer and the 3-2 positive electrode mixture layer.

In this case, the thickness of the first positive electrode mixture layer and the second positive electrode mixture layer and the third positive electrode mixture layer may be similar to each other by adjusting the coating thickness of the first positive electrode slurry and the second positive electrode slurry.

As another example, after forming the first positive electrode mixture layer by applying the first positive electrode slurry to the core part of one positive electrode current collector, the second positive electrode slurry was applied to the coated part and the uncoated part on the first positive electrode mixture layer of the core part. And the second positive electrode slurry may be applied to the outer portion to integrally form the second positive electrode mixture layer and the third positive electrode mixture layer.

In this case, the coating thickness of the third positive electrode mixture layer may be thicker than the coating thickness of the second positive electrode mixture layer. In other words, when forming the third positive electrode mixture layer than when forming the second positive electrode mixture layer, the applied thickness of the second positive electrode slurry is made thicker, so that the combined thickness of the first positive electrode mixture layer and the second positive electrode mixture layer is obtained. The thickness of the third positive electrode mixture layer can be similarly formed.

In addition to this manufacturing method, as long as it can have the same structure as the above-described structure, it is not limited.

Regardless of which method is manufactured, the combined thickness of the first positive electrode mixture layer and the second positive electrode mixture layer and the thickness of the third positive electrode mixture layer may be similar, but is not limited, but in detail, the thickness of the third positive electrode mixture layer May be equal to or smaller than the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer.

Specifically, the third positive electrode mixture layer has the same thickness as the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer so as not to form an additional space in the electrode assembly in a wound form to prevent capacity reduction. Can have.

In this case, since the ratio of the volume of the active material contained in the same space increases in terms of energy density, it is preferable.

Meanwhile, depending on the Si-based content, the third positive electrode mixture layer may be formed to have a thickness smaller than the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer.

Specifically, when the Si-based content increases and the degree of volume expansion is severe, it is good if a space for storing the electrolyte solution is provided throughout the electrode assembly, so that the thickness of the third positive electrode mixture layer is the thickness of the first positive electrode mixture layer. If it is less than the sum of the thicknesses of the second positive electrode material layer and the second positive electrode material mixture layer, since a space can be provided in a wound form, it is effective. However, even in this case, in order to minimize the decrease in energy density, the thickness of the third positive electrode mixture layer is within 0.5 to 3 μm compared to that of the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer. It can have a thickness difference.

Outside the above range, if the thickness difference is too large, the energy density may be lowered, which is not preferable.

Specifically, when the content of the Si-based material is 5% to 30% by weight, the thickness of the third positive electrode mixture layer may be the same as the combined thickness of the first positive electrode mixture layer and the second positive electrode mixture layer, and the Si-based material When the content of the material is 30% by weight or more, the thickness of the third positive electrode mixture layer may be smaller than the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer.

In addition, the positive electrode of the present invention may have a specific structure in consideration of the effect intended by the present invention, that is, the formation of an electrolyte storage space and minimization of a decrease in energy density.

First, unlike the first positive electrode mixture layer that is entirely applied from the core part, the thickness of the second positive electrode mixture layer having an uncoated part may be thinner, and specifically, the thickness of the first positive electrode mixture layer is 30 μm to 150 Μm, and the thickness of the second positive electrode mixture layer may be 4 μm to 50 μm in a range smaller than the thickness of the first positive electrode mixture layer.

More specifically, the thickness ratio of the first positive electrode mixture layer and the second positive electrode mixture layer may be 9:1 to 3:1, and in detail, 7:1 to 5:1.

Outside the above range, when the second positive electrode mixture layer becomes thick, the space for storing the electrolyte increases, but relatively, the volume ratio of the active material layer to the total volume decreases, and the energy density decreases, which is not preferable. , If it is too thin, the effect intended in the present invention, that is, the storage property of the electrolyte solution, and life characteristics and safety cannot be secured, which is not preferable.

Accordingly, the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer may be selected to satisfy the above ratio within the specific range.

Second, the width of the uncoated portion may be 0.1mm to 1mm, and in detail, it may be 0.5mm to 1mm.

The width means the length in the winding direction, and when the coated portion and the uncoated portion are coated in a cross-arranged form, it means the length in the cross-arranged direction.

In addition, the distance of each of the uncoated portions, that is, the width of the applied portion may be 1mm to 10mm.

Outside the above range, when the width of the uncoated portion is too large or the gap is too small, the area occupied by the uncoated portion is too large, and the portion occupied by the active material layer is relatively reduced, which is not preferable in terms of energy density, If the width of the uncoated portion is too small or the gap is too wide, the uncoated portion is formed too little, and the practical effect according to the present invention cannot be obtained, which is not preferable.

Accordingly, it is preferable that the uncoated portion has an area greater than or equal to a certain portion of the area in which the entire second positive electrode mixture layer is formed, and specifically, the cross-sectional area of the uncoated portion is based on the entire area of the coated portion and the uncoated portion, It may be 1% to 20%, specifically, it may be 5% to 15%.

The application form of the second positive electrode mixture layer is not limited, and if a form including an uncoated part and an applied part, an uncoated part may be formed in various forms, for example, a line shape (stripe shape), a circular shape, or a polygonal shape. .

However, in consideration of the easiness of the process, the applied part and the uncoated part may be in the form of stripes in a form in which the applied part and the non-applied part are alternately arranged in a line form, and the interval may be constant or may not be constant.

Meanwhile, a positive electrode active material may be included in the first positive electrode mixture layer, the second positive electrode mixture layer, and the third positive electrode mixture layer, and the positive electrode active material is, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide ( A layered compound such as LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxides such as formula Li _1+x Mn _2-x O ₄ (wherein x is 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 , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O _7; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (here, 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, Zn or Ta, and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, A lithium manganese composite oxide represented by Ni, Cu, or Zn); _{LiMn 2} O _{4 in} which part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; It _{may be a material selected from Fe 2} (MoO ₄ ) ₃ and the like, and may include an active material disclosed in the art.

Accordingly, active materials included in the first positive electrode mixture layer, the second positive electrode mixture layer, and the third positive electrode mixture layer may be selected according to the purpose of use of the battery, and in detail, for ease of the process, all may have the same composition. .

In addition to the positive electrode active material, a conductive material, a binder, and a filler may be further included in each of the positive electrode mixture layers. As described.

The positive electrode current collector is generally manufactured to a thickness of 3 to 200 μm, and is not particularly limited as long as it has high conductivity without causing chemical changes to the battery. For example, stainless steel, aluminum, nickel, Titanium, and one selected from among those surface-treated with carbon, nickel, titanium, or silver on the surface of aluminum or stainless steel may be used, and in detail, aluminum may be used. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

Separator

As the separator having a long sheet structure interposed between the anode and the cathode, 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 µm, and the thickness is generally 5 to 300 µm. Examples of such a separation membrane include olefin-based polymers such as polypropylene having chemical resistance and hydrophobic properties; Sheets or non-woven fabrics made of glass fiber or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

Secondary battery

According to the invention, also,

There is provided a secondary battery having a structure in which the jelly-roll type electrode assembly is impregnated with a lithium-containing non-aqueous electrolyte and is embedded in a cylindrical or rectangular metal battery case. That is, the secondary battery may be a lithium secondary battery.

The lithium-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt.

Examples of the non-aqueous electrolyte solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, aceto Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid tryster, trimethoxy methane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative , Tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate, and other aprotic organic solvents may be used.

The lithium salt is a material 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.

In some cases, an organic solid electrolyte, an inorganic solid electrolyte, or the like may be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, ions A polymer or the like containing a sex dissociation group can be used.

As the inorganic solid electrolyte, for example, 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, Li ₃ PO ₄ -Li ₂ S-SiS _{2 may be used.}

In addition, non-aqueous electrolytes include pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide for the purpose of improving charge/discharge properties and flame retardancy, etc. , Nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. May be. In some cases, in order to impart non-flammability, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included in order to improve high-temperature storage characteristics.

The structure of the cylindrical or prismatic metal battery case is disclosed in the art, and a description thereof will be omitted in the present specification.

Lithium secondary batteries of this structure are various devices such as mobile phones, portable computers, smart phones, tablet PCs, smart pads, netbooks, LEVs (Light Electronic Vehicles), electric vehicles, hybrid electric vehicles, plug-ins. It can be used as a unit cell such as a hybrid electric vehicle and a power storage device.

As described above, the jelly-roll type electrode assembly according to the present invention provides a space for storing an electrolyte even if the electrode assembly is compressed when the electrode assembly is squeezed during volume expansion of the electrode assembly by multilayer coating and pattern coating on the core portion of the anode. I can. Accordingly, it is possible to improve the safety and life characteristics of a secondary battery including the electrolyte by preventing the electrolyte solution from being pulled to the outside, while minimizing a decrease in capacity due to a decrease in energy density.

1 is a schematic view of a vertical cross-sectional view before winding of a jelly-roll type electrode assembly according to an embodiment of the present invention;
2 is a schematic view of a vertical cross-sectional view before winding of a jelly-roll type electrode assembly according to another embodiment of the present invention;
3 is a schematic view of a vertical cross-sectional view before winding of a jelly-roll type electrode assembly according to another embodiment of the present invention;
4 is a schematic view of a vertical cross-sectional view before winding of a jelly-roll type electrode assembly according to another embodiment of the present invention;
5 is a schematic view of a vertical cross-sectional view of a jelly-roll type electrode assembly before winding according to another embodiment of the present invention.

Hereinafter, it will be described with reference to the drawings according to an embodiment of the present invention, but this is for an easier understanding of the present invention, and the scope of the present invention is not limited thereto.

1 is a schematic diagram of a jelly-roll type electrode assembly (hereinafter, referred to as “jelly-roll”) according to an embodiment of the present invention before winding.

Referring to FIG. 1, the jelly-roll type electrode assembly 100 according to the present invention has a structure in which a separator 130 is interposed between an anode 110 and a cathode 120 and is wound in the direction of an arrow.

Here, the positive electrode 110 includes a core portion and an outer portion, and as a whole, has a structure in which positive electrode mixture layers 111, 112, and 113 are formed on the positive electrode current collector 101.

At this time, the core portion and the outer portion are divided based on the length l from the winding point of the electrode assembly to the winding end point, and the core portion is formed within 50% of the total length l from the winding point.

On the other hand, the positive electrode current collector 101 is disclosed as an integrally formed structure, but may have a shape that is separated from the core portion and the outer portion.

However, in the following, even when formed as an integral part, in order to divide the core portion and the outer portion, the first positive electrode current collector and the second positive electrode current collector are classified and named.

Referring back to FIG. 1, FIG. 1 discloses a configuration in which a first positive electrode mixture layer, a second positive electrode mixture layer, and a third positive electrode mixture layer are formed separately.

Specifically, the core portion forms the first positive electrode mixture layer 111 by applying a positive electrode slurry on the first positive electrode current collector, and the second positive electrode mixture layer ( 112).

In this case, the second positive electrode mixture layer 112 is formed on a part of the first positive electrode mixture layer 111. Specifically, the first positive electrode mixture layer 111 has a pattern-coated structure to have a coating portion 112a to which a positive electrode slurry containing a positive electrode active material is applied and an uncoated portion 112b to which the slurry is not applied.

At this time, in consideration of minimization of electrolyte storage and energy density reduction, the first positive electrode mixture layer 111 and the second positive electrode mixture layer 112 are specifically designed.

In one example, the thickness (t ₁ ) of the first positive electrode mixture layer 111 is 30 μm to 150 μm, and the thickness (t ₂ ) of the second positive electrode mixture layer 1112 is the first positive electrode mixture layer 111 In a range smaller than the thickness of ), it may be 4 μm to 50 μm.

Moreover, the ratio (t1:t2) of the thickness t1 of the first positive electrode mixture layer 111 and the thickness t2 of the second positive electrode mixture layer 112 may be 9:1 to 3:1, In detail, the bar may be 7:1 to 5:1, and may be selected to satisfy the ratio in the thickness range.

In another example, the width g of the uncoated portion 112b on which the second positive electrode mixture layer 112 is not formed may be 0.1 mm to 1 mm, and in detail, 0.5 mm to 1 mm.

In addition, the distance between each of the uncoated portions 112b, that is, the width w of the coated portions 112a may be 1mm to 10mm.

Meanwhile, a third positive electrode mixture layer 113 is formed by applying a positive electrode slurry on the second positive electrode current collector at the outer portion.

_{At this time, the third positive electrode mixture layer 113 is a thickness (t 1} ) of the first positive electrode mixture layer 111 and a second positive electrode mixture so as not to form an additional space in the electrode assembly in a wound form to prevent capacity reduction. It has the same thickness (t ₃ ) as the sum of the thicknesses (t _{2) of the layer 112.}

On the other hand, the negative electrode 120 has a negative electrode mixture layer 121 including a negative active material is formed on both sides of the negative electrode current collector 102, wherein the negative active material is a Si-based material based on the total weight of the negative active material 5 It may be included in a weight percent or more.

In another specific example, the structure as shown in FIG. 1, but the thickness of the third positive electrode mixture layer may be formed to have a thickness smaller than the sum of the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer. This structure is shown in FIG. 2.

Referring to FIG. 2, the remaining codes are numbered in a manner similar to that of FIG. 1 as 200.

Specifically, the jelly-roll type electrode assembly 200 has a structure in which the separator 230 is interposed between the anode 210 and the cathode 220 and is wound in the direction of the arrow.

Here, the positive electrode 210 includes positive electrode mixture layers 211, 212, and 213 including a positive electrode active material formed on both surfaces of the positive electrode current collector 201, and specifically, on the first positive electrode current collector of the core part. A first positive electrode mixture layer 211 is formed, and a second positive electrode mixture layer 212 is formed on the first positive electrode mixture layer 211.

In addition, a third positive electrode mixture layer 213 is formed on the second positive electrode current collector in the outer portion.

However, in comparison with the first, the third thickness (T ₃₎ of the positive electrode mixture layer 213 has a thickness (T of the thickness of the first positive electrode material mixture layer (211), (T ₁₎ and the second positive electrode mixture layer 212 _It is smaller by _{d 1} than the sum of 2 ). In this case, d ₁ may be 0.5 to 3 μm.

In this case, it is possible to create a space for storing the electrolyte solution as a whole of the positive electrode, which is more preferable when the volume change due to charge and discharge is very large.

On the other hand, the negative electrode 220, as described in Figure 1, the negative electrode mixture layer 221 including a negative electrode active material is formed on both sides of the negative electrode current collector 202, wherein the negative electrode active material is a Si-based material Based on the total weight of the negative active material, for example, 5% by weight may be included, and in detail, it may be included in an amount of 10% by weight or more.

Meanwhile, in FIGS. 3 to 5 below, schematic diagrams before winding of the jelly-roll type electrode assemblies 300, 400, 500 according to another embodiment of the present invention are shown.

At this time, the detailed contents of FIGS. 3 to 5 are the same as those of FIGS. 1 to 2, but are illustrated to show differences according to the manufacturing method.

First, referring to FIG. 3, the jelly-roll type electrode assembly 300 has a structure in which a separator 330 is interposed between an anode 310 and a cathode 320 and is wound in the direction of an arrow.

Here, the positive electrode 310 includes positive electrode mixture layers 311, 312, and 313 including a positive electrode active material formed on both surfaces of the positive electrode current collector 301, and specifically, on the first positive electrode current collector of the core part. A first positive electrode mixture layer 311 is formed, a second positive electrode mixture layer 312 is formed on the first positive electrode mixture layer 311, and a third positive electrode is formed on the second positive electrode current collector in the outer portion. It is the same as the jelly-roll electrode assemblies 100 and 200 of FIGS. 1 to 2 in that it has a structure in which the mixture layer 313 is formed.

However, in the jelly-roll type electrode assembly 300 according to FIG. 3, the positive electrode slurry is first applied entirely on the positive electrode current collector of the core part and the outer part, but when applying the positive electrode slurry, the part corresponding to the outer part rather than the core part By applying the positive electrode slurry to a thicker layer, the thickness of the first positive electrode mixture layer 311 may be smaller than the thickness of the third positive electrode mixture layer 313. That is, in FIG. 3, the first positive electrode mixture layer 311 and the third positive electrode mixture layer 313 are integrally formed.

In addition, a positive electrode slurry is additionally applied on the first positive electrode mixture layer 311, and a second positive electrode mixture layer 312 is formed to include an applied portion and an uncoated portion to manufacture the positive electrode 310.

Next, referring to FIG. 4, the jelly-roll type electrode assembly 400 is wound in the direction of the arrow with the separator 430 interposed between the anode 410 and the cathode 420.

Here, the positive electrode 410 includes positive electrode mixture layers 411, 412, and 413 including a positive electrode active material formed on both surfaces of the positive electrode current collector 401, and specifically, on the first positive electrode current collector of the core part. A first positive electrode mixture layer 411 is formed, a second positive electrode mixture layer 412 is formed on the first positive electrode mixture layer 411, and a third positive electrode is formed on the second positive electrode current collector in the outer portion. It is the same as the jelly-roll type electrode assemblies 100 and 200 of FIGS. 1 to 2 in that it has a structure in which the mixture layer 413 is formed.

However, in the jelly-roll type electrode assembly 400 according to FIG. 4, a positive electrode slurry is first applied to the entire core portion and the outer portion of the positive electrode current collector 401 so that the first positive electrode mixture layer 411 and the third-first positive electrode mixture layer 411 are applied. A positive electrode mixture layer 413-1 is formed, and a second positive electrode mixture layer 412 is formed by forming a positive electrode slurry to include an applied portion and an uncoated portion again on the first positive electrode mixture layer 411 of the core portion. On the negative 3-1 positive electrode mixture layer 413-1, a positive electrode slurry is entirely applied to form the 3-2 positive electrode mixture layer 413-2, thereby manufacturing the positive electrode 410. In this case, the third positive electrode mixture layer 413 refers to the entire 3-1 positive electrode mixture layer 413-1 and the 3-2th positive electrode mixture layer 413-2.

Finally, referring to FIG. 5, the jelly-roll type electrode assembly 500 has a structure in which a separator 530 is interposed between an anode 510 and a cathode 520 and is wound in the direction of an arrow.

Here, the positive electrode 510 includes positive electrode mixture layers 511, 512, and 513 including a positive electrode active material formed on both surfaces of the positive electrode current collector 501, and specifically, on the first positive electrode current collector of the core part. A first positive electrode mixture layer 511 is formed, a second positive electrode mixture layer 512 is formed on the first positive electrode mixture layer 511, and a third positive electrode is formed on the second positive electrode current collector of the outer portion. It is the same as the jelly-roll type electrode assemblies 100 and 200 of FIGS. 1 to 2 in that it has a structure in which the mixture layer 513 is formed.

However, in the jelly-roll type electrode assembly 500 according to FIG. 5, the first positive electrode mixture layer 511 is formed by applying the positive electrode slurry to the positive electrode current collector only on the core part, and the positive electrode slurry is again mixed with the first positive electrode mixture in the core part. The second positive electrode mixture layer 512 and the third positive electrode mixture layer 513 may be integrally formed by forming on the layer 511 to include an applied portion and an uncoated portion, and by applying the entire outer portion.

Hereinafter, the present invention will be described in more detail through examples, but the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

<Production Example 1>

Preparation of positive electrode slurry

_{LiNi 1/3} Mn _1/3 Co _1/3 O ₂ is used as a positive electrode active material, and a conductive material (carbon black) and a binder (PVdF) are each NMP (N-methyl-2- pyrrolidone) and mixed to prepare a positive electrode slurry.

<Example 1>

Manufacture of anode

The positive electrode slurry prepared in Preparation Example 1 was coated on both sides of an aluminum foil having a thickness of 15 μm to a thickness of 100 μm to form a first coating layer. Thereafter, the same positive electrode slurry was applied on both sides of the first coating layer on both sides of the first coating layer at a length of about 30% from one side based on the total length of the aluminum foil, so that the width of the coated part/uncoated part was The pattern was coated to be 10mm/1mm, and a second coating layer was formed by coating the entire first coating layer in a portion corresponding to the remaining 70% to a thickness of 20 μm, followed by drying and rolling to prepare a positive electrode.

Preparation of cathode

As the negative electrode active material, a mixture of 90% by weight: 10% by weight of artificial graphite and SiO is used, and the mixture, a conductive material (carbon black), and a binder (PVdF) are mixed with NMP (N- methyl-2-pyrrolidone) and mixed to prepare a negative electrode slurry.

The negative electrode slurry was coated on both sides of a 15 μm-thick copper foil to a thickness of 100 μm, dried, and rolled to prepare a negative electrode.

Preparation of jelly-roll type electrode assembly

A separator having a long sheet structure of polyethylene was interposed between the negative electrode and the positive electrode, and as shown in FIG. 1, a jelly-roll type electrode assembly was prepared by winding the surface on which the negative electrode mixture prepared in Preparation Example 5 was formed to be the winding inner surface.

Manufacturing of secondary battery

The jelly-roll type electrode assembly is housed in a cylindrical battery case, ethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate are mixed at a volume ratio of 1:1:1, and containing _{1 M of LiPF 6 as a lithium salt.} A cylindrical secondary battery was manufactured by adding a non-aqueous electrolyte.

<Example 2>

In Example 1, the same as in Example 1, except that the second coating layer was formed to have a thickness of 18 μm on the first coating layer of the remaining 70% when the second coating layer was formed. -A roll-type electrode assembly and a cylindrical secondary battery were prepared.

<Comparative Example 1>

In Example 1, the same as in Example 1, except that the positive electrode slurry prepared in Preparation Example 1 was coated on both sides of an aluminum foil having a thickness of 15 µm to a thickness of 120 µm to produce a positive electrode. And a cylindrical secondary battery.

<Comparative Example 2>

In Example 1, after forming the first coating layer, the same positive electrode slurry was pattern-coated on the first coating layer with a thickness of 20 μm each so that the width of the coated part/uncoated part was 10 mm/1 mm. A jelly-roll type electrode assembly and a cylindrical secondary battery were manufactured in the same manner as in Example 1, except that a positive electrode was manufactured by drying and rolling after forming the coating layer.

<Experimental Example 1> (Capacity and life characteristics)

The secondary batteries each prepared in Examples 1 to 2 and Comparative Examples 1 to 2 were repeated 130 times under a condition of 1.0C in a voltage range of 2.5V to 4.2V, and the discharge capacity was measured to compare the initial capacity and the initial cycle. The capacity retention rate (%) was measured, and the results are shown in Table 1 below.

Initial capacity Capacity retention rate (%) Example 1 5585mAh (100%) 95.4(130cycle) Example 2 5598mAh (100%) 95.1(130cycle) Comparative Example 1 5572mAh (100%) 82.8%(130cycle) Comparative Example 2 5554mAh (100%) 93.9%(130cycle)

Referring to Table 1, when using the electrode assembly of the present invention according to Examples 1 and 2, compared to Comparative Example 1 without pattern coating, it can be seen that it exhibits excellent life characteristics. On the other hand, of Comparative Example 2 In this case, the life characteristics are similar to those of Examples 1 and 2, but referring to the initial discharge capacity, it can be seen that the capacity is decreased.

Those of ordinary skill in the field to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Claims (12)

In the jelly-roll type electrode assembly wound with a separator interposed between an anode and a cathode,
The anode includes a core portion and an outer portion,
The core part includes a first positive electrode current collector, a first positive electrode mixture layer disposed on the first positive electrode current collector, and a second positive electrode mixture layer disposed on the first positive electrode mixture layer,
The outer portion includes a second positive electrode current collector and a third positive electrode mixture layer positioned on the second positive electrode current collector,
The second positive electrode mixture layer is an electrode assembly having an applied portion and an uncoated portion. The method of claim 1,
The core part is an electrode assembly formed within 50% of the total length from the winding time point based on the length from the winding time point to the winding end point of the electrode assembly. The jelly of claim 1, wherein the thickness of the first positive electrode mixture layer is 30 μm to 150 μm, and the thickness of the second positive electrode mixture layer is 4 μm to 50 μm in a range smaller than that of the first positive electrode mixture layer. Roll-type electrode assembly. The jelly-roll type electrode assembly of claim 1, wherein a thickness ratio of the first positive electrode mixture layer and the second positive electrode mixture layer is 9:1 to 3:1. The jelly-roll type electrode assembly of claim 1, wherein the uncoated portion has a width of 0.1mm to 1mm. The jelly-roll type electrode assembly of claim 1, wherein the distance of each of the uncoated portions is 1mm to 10mm. The jelly-roll type electrode assembly of claim 1, wherein the thickness of the third positive electrode mixture layer is equal to or smaller than the thickness of the first positive electrode mixture layer and the thickness of the second positive electrode mixture layer. The jelly-roll type electrode assembly of claim 7, wherein the thickness of the third positive electrode mixture layer is 0.5 μm to 3 μm smaller than that of the combined thickness of the first positive electrode mixture layer and the second positive electrode mixture layer. The jelly-roll type electrode assembly of claim 1, wherein the composition of the positive electrode active material included in the first positive electrode mixture layer, the second positive electrode mixture layer, and the third positive electrode mixture layer is the same. The method of claim 1,
The negative electrode includes a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector, and the negative electrode mixture layer comprises a Si-based material. The method of claim 10, wherein the Si-based material is a Si/C composite, SiO _x (0<x<2), metal-doped SiO _x (0<x<2), SiO _x /C(0<x< 2), a jelly-roll type electrode assembly of one or more selected from the group consisting of pure Si (pure Si), and Si alloy (Si-alloy). A secondary battery having a structure in which the jelly-roll type electrode assembly according to any one of claims 1 to 11 is impregnated with a lithium-containing non-aqueous electrolyte and is embedded in a cylindrical or rectangular metal battery case.

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