KR102227802B1 - Electrode active material slurry composition and secondary battery comprising electrode using the same - Google Patents

Abstract

The present invention relates to an electrode active material slurry composition including an electrode active material, an ion conductive polymer, a non-aqueous additive, and a ceramic electrolyte, an electrode for a lithium secondary battery including the same, and a lithium secondary battery.

Description

Electrode active material slurry composition and lithium secondary battery including an electrode using the same {ELECTRODE ACTIVE MATERIAL SLURRY COMPOSITION AND SECONDARY BATTERY COMPRISING ELECTRODE USING THE SAME}

The present invention relates to an electrode active material slurry composition having improved ion conductivity improvement effect, an electrode for a lithium secondary battery using the same, and a lithium secondary battery including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and among secondary batteries, lithium secondary batteries exhibit high energy density and operating potential, have a long cycle life, and have a low self-discharge rate. Has been commercialized and widely commercialized.

In general, a lithium secondary battery is composed of a positive electrode and a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte solution in which a lithium salt is dissolved in an organic solvent, and the positive electrode and the negative electrode contain an electrode active material on each electrode current collector. It is prepared by applying the containing electrode slurry composition, followed by drying and rolling (press).

On the other hand, as the need for a high-capacity battery increases, in order to further maximize the thickness uniformity of the electrode mixture layer and the energy density in the electrode, the pressure applied during the rolling process increases, causing the active material particles to be destroyed, or Intensified pressing causes a problem in that the ratio of pores inside the electrode mixture layer decreases.

When the porosity ratio decreases in this way, the impregnation of the electrolyte solution to the inside of the electrode becomes difficult, so that it is difficult to secure an ion migration path, and the ion conductivity decreases. As a result, the rate characteristics of the battery are reduced, and the battery performance and life characteristics are deteriorated.

Therefore, to increase the density of the electrode, while increasing the capacity characteristics of the battery, while realizing the effective adhesion between the electrode current collector and the electrode mixture layer, and at the same time, the electrode design that can secure the ion migration path inside the electrode mixture layer even after the rolling process. Is necessary.

Republic of Korea Patent Publication No. 10-2016-0038080

In order to solve the above problems,

An object of the present invention is to provide an electrode active material slurry composition having improved ion conductivity.

In addition, a second technical problem of the present invention is to provide an electrode for a lithium secondary battery manufactured using the electrode active material slurry composition.

In addition, a third technical problem of the present invention is to provide a lithium secondary battery including the lithium secondary battery electrode.

Specifically, in one embodiment of the present invention

Electrode active material;

Ion conductive polymers including polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP);

Non-aqueous additives; And

Contains a solvent;

The ion conductive polymer provides an electrode active material slurry composition included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition.

In addition, the non-aqueous additive may include tetraethylene glycol dimethyl ether (TEGDME), and may be included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition.

In addition, the electrode active material slurry composition of the present invention may further include a ceramic electrolyte.

The ceramic electrolyte may include a phosphate-based material represented by the following formula (1).

[Formula 1]

Li _{1 + x} Al _x Ge _{2 - x} (PO ₄ ) ₃ (0 <x <1)

Specifically, the ceramic electrolyte may include lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ; LAGP), in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition Can be included as.

In addition, in an embodiment of the present invention

Electrode current collector; And

It provides an electrode for a lithium secondary battery comprising; an electrode mixture layer positioned on at least one surface of the electrode current collector and formed by applying and drying the electrode active material slurry composition of the present invention.

In this case, the electrode may be an anode or a cathode.

In addition, in an embodiment of the present invention

In a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte,

At least one electrode of the positive electrode or the negative electrode provides a lithium secondary battery including the electrode according to the present invention.

In the present invention, by including an additive that can serve as an ion transfer path to secure adhesion between electrode active materials or between an electrode mixture and an electrode current collector when preparing an electrode slurry composition, internal resistance is reduced and high rate characteristics are improved for lithium secondary batteries. An electrode and a lithium secondary battery having the same can be manufactured.

1 is a cross-sectional view of an electrode mixture layer formed using the electrode active material slurry composition of the present invention.
2 is a graph showing results of measuring internal interface resistance characteristics of secondary batteries of Examples 7 to 9 and Comparative Examples 7 to 9;
3 is a graph showing the results of measuring the resistance characteristics of the secondary battery cells of Example 9 and Comparative Example 7.

Hereinafter, the present invention will be described in more detail.

The terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Conventional secondary battery electrodes are manufactured by preparing an electrode active material slurry, then coating it on an electrode current collector, drying, and rolling. In this case, when high pressure is applied to increase the packing density of the electrode in the rolling process, the pressure inside the electrode active material mixture layer is intensified, and there is a disadvantage that the ratio of pores inside the electrode mixture layer decreases. As a result, as it becomes difficult to impregnate the electrolyte to the inside of the electrode, it is not possible to secure an ion migration path, so that the ion conductivity is lowered, and consequently, the rate characteristic is reduced, resulting in a decrease in battery performance and lifespan characteristics.

Accordingly, in the present invention, by further including an electrolyte used in the gel polymer electrolyte when preparing the electrode active material slurry composition as an additive, lithium, which can realize the effect of improving ion conductivity by maintaining and securing the voids inside the electrode mixture layer even after the rolling process. It is possible to manufacture an electrode for a secondary battery and a lithium secondary battery having the same.

Specifically, in one embodiment of the present invention

Electrode active material;

Ion conductive polymers including polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP);

Non-aqueous additives; And

Contains a solvent;

The ion conductive polymer provides an electrode active material slurry composition included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition.

First, the electrode active material slurry composition of the present invention may include at least one of a negative electrode active material slurry composition and a positive electrode active material slurry composition.

Accordingly, the electrode active material slurry may include at least one of a positive electrode active material and a negative electrode active material according to the type of the electrode active material slurry composition.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include at least one metal such as cobalt, manganese, nickel, or aluminum, and a lithium composite metal oxide containing lithium. have.

More specifically, the lithium composite metal oxide is a lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ Etc.), lithium-cobalt-based oxides (e.g., LiCoO ₂ etc.), lithium-nickel-based oxides (e.g., LiNiO ₂ etc.), lithium-nickel-manganese-based oxides (e.g., LiNi _{1 -Y} Mn _Y O ₂ (where, 0 <Y <1), LiMn _2-z Ni _z O ₄ (where, 0 <Z <2) and the like), lithium-nickel-cobalt-based oxide (for example, LiNi _{1- Y1} Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese-cobalt oxide (e.g., LiCo _{1 - Y2} Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _{2 - z1} Co _z1 O ₄ (here, 0<Z1<2), etc.), lithium-nickel-manganese-cobalt oxide (for example, Li(Ni _P Co _Q Mn _R )O ₂ (here, 0 <P<1, 0<Q<1, 0<R<1, P+Q+R=1) or Li(Ni _P1 Co _Q1 Mn _R1 )O ₄ (here, 0<P1<2, 0<Q1 <2, 0<R1<2, P1+Q1+R1=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni _P2 Co _Q2 Mn _R2 M _S2 ) O ₂ (Wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and P2, Q2, R2 and S2 are the atomic fractions of independent elements, respectively, 0<P2< 1, 0<Q2<1, 0<R2<1, 0<S2<1, P2+Q2+R2+S2=1, etc.) have. _{Among these, the lithium composite metal oxide is LiCoO 2} , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (e.g., Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ ) in that it can increase the capacity characteristics and stability of the battery. , LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ , or LiNi _{0 . 8} Mn _{0 . 1} Co _{0 . 1} O _2), or lithium nickel cobalt aluminum oxide _{(e.g., LiNi 0. 8 Co 0.} 15 Al 0. 05 O 2 , etc.) and the like, the kind and amount of constituent elements forming the lithium composite metal oxide Considering the remarkable improvement effect according to the ratio control, the lithium composite metal oxide is LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _{0 . 7} Mn _{0 . 15} Co _{0 . 15} O ₂ or LiNi _{0 . 8} Mn _{0 . 1} Co _{0 . It} may be 1 O ₂ or the like, and any one or a mixture of two or more of them may be used.

In addition, in the lithium composite metal oxide, at least one of the metal elements other than lithium is selected from the group consisting of W, Mo Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb. It may be doped with any one or two or more elements. When the above-described metal element is further doped into the lithium-defective lithium composite metal oxide as described above, the structural stability of the positive electrode active material is improved, and as a result, the output characteristics of the battery may be improved. In this case, the content of the doping element contained in the lithium composite metal oxide may be appropriately adjusted within a range not deteriorating the characteristics of the positive electrode active material, and specifically, may be 0.02 atomic% or less.

The negative electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; Metal oxides capable of doping and undoping lithium such as SiO _x1 (0 <x1 <2), SnO _{2, vanadium oxide, and lithium vanadium oxide;} Or a composite including the metal compound and a carbonaceous material, such as a Si-C composite or an Sn-C composite, and any one or a mixture of two or more of them may be used. In addition, a metal lithium thin film may be used as the negative electrode active material. Further, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. As low crystalline carbon, soft carbon and hard carbon are typical, and high crystalline carbon is amorphous, plate, scale, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish). graphite), pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes) is typical.

The electrode active material may be included in an amount of 80 to 99% by weight based on the total weight of the electrode active material slurry composition. If the content of the electrode active material is less than 80% by weight, the capacity characteristics of the battery decrease, and if it exceeds 99% by weight, the contact probability between the electrode active material and the conductive material decreases due to a relatively decrease in the content of the conductive material, and the increase of the electrically inactive active material. The output characteristics of the battery may be deteriorated.

In addition, in the electrode active material slurry composition of the present invention, the ion conductive polymer may include polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP) that can simultaneously serve as a binder. I can.

The ion conductive polymer may be included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition. If the content of the ion conductive polymer is less than 0.1% by weight, the electrode active material layer may be detached due to a decrease in adhesion between the electrode active material and the electrode current collector, and if it exceeds 5% by weight, the resistance increases, as well as, Relatively, the output characteristics of the battery may be deteriorated due to a decrease in the content of the electrode active material.

In addition, in the electrode active material slurry composition of the present invention, the non-aqueous additive may include tetraethylene glycol dimethyl ether (TEGDME) serving as an ion transport channel.

The non-aqueous additive may be included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition. At this time, if the content of the non-aqueous additive is less than 0.1% by weight, the adhesion between the electrode mixture layer and the electrode current collector may decrease, and if it exceeds 5% by weight, not only the resistance increases, but also the content of the electrode active material relatively decreases. The output characteristics of the furnace battery may be deteriorated.

In addition, the electrode active material slurry composition of the present invention may further include a ceramic electrolyte serving as an ion transfer passage.

The ceramic electrolyte may include a phosphate-based material represented by Formula 1 below.

[Formula 1]

Li _{1 + x} Al _x Ge _{2 - x} (PO ₄ ) ₃ (0 <x <1)

Specifically, the ceramic electrolyte may include lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ; LAGP), in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition Can be included as.

At this time, if the content of the ceramic electrolyte is less than 0.1% by weight, the effect of securing the ion migration path is insufficient, and if it exceeds 5% by weight, the resistance increases, and the output characteristics of the battery decrease due to a relatively decrease in the content of the electrode active material. Can be.

In the electrode active material slurry composition of the present invention, the solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and the electrode active material, ion conductive polymer, non-aqueous additive, and optional It may be included to have a desirable viscosity according to the type of ceramic electrolyte. For example, it may be included so that the concentration of the solid content including the electrode active material, the ion conductive polymer, the non-aqueous additive, and optionally the ceramic electrolyte is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

In the case of using an excessive amount of binder in order to secure adhesion during the production of conventional electrode active material slurry, not only the ratio of the electrode active material is reduced, but also the binder itself acts as a resistance element in the electrode, reducing the voltage, thereby reducing the performance of the battery. There is. In addition, there is a problem that the process efficiency decreases due to a long mixing time, and due to a side reaction with an electrolyte, capacity reduction and cell resistance increase are accelerated during high temperature storage. However, when the binder content is reduced, it is difficult to secure adhesion between the electrode current collector and the electrode assembly layer, thereby causing electrode peeling in the drying and pressing process for manufacturing the electrode, thereby increasing the electrode defect rate. In addition, peeling of the electrode may occur due to external impact, which has a disadvantage of adversely affecting stability such as life characteristics of the battery.

In the present invention, when preparing an electrode active material slurry composition, by including an ion conductive polymer that can act as a binder, a non-aqueous additive that can serve as an ion transfer path, and a ceramic electrolyte, the adhesion between the electrode active material and the electrode current collector is secured. In addition, it is possible to achieve an effect of securing an ion migration path and a reduction in resistance of the electrode interface even after the rolling process.

In addition, the electrode active material slurry composition of the present invention may optionally further include a conductive material and a filler in addition to the above components.

The conductive material is not particularly limited as long as it has conductivity without causing chemical changes to the battery, and for example, it may further include heterogeneous conductive materials having different shapes such as particles, fibers, or plates, and electrode active material slurry It may be included in 0.2 to 30% by weight, specifically 1 to 10% by weight, based on the total weight of the composition.

Specifically, the particulate conductive material can be used without special restrictions as long as it has conductivity and satisfies the morphological conditions, but considering the excellent improvement effect of the use of the particulate conductive material, the particulate conductive material is natural graphite or artificial graphite. Graphite such as; Carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc., or denka black may be used, and any one or a mixture of two or more of them may be used.

When the conductive material is a particulate conductive material, specifically, the average particle diameter (D ₅₀ ) may be 10 to 45 nm, and a specific surface area may be 40 to 170 m ² /g. If the average particle diameter of the particulate conductive material is less than 10 nm or the specific surface area exceeds 170 m ² /g, the dispersibility in the positive electrode mixture is greatly reduced due to aggregation of the particulate conductive material, and the average particle diameter exceeds 45 nm or If the surface area is less than 40 m ² /g, the size is too large, and therefore, in the arrangement of the conductive material according to the porosity of the positive electrode active material, it may not be uniformly dispersed throughout the positive electrode mixture and may be partially biased.

The fibrous or plate-like conductive material is a conductive material having an aggregate structure whose two sides corresponding to each other are flat and the size in the horizontal direction is larger than the size in the vertical direction. ) Phase, scale phase, etc. may also be included. The fibrous or plate-shaped conductive material may be a conductive fiber such as carbon fiber or metal fiber.

In addition, the conductive material may include 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.

When a heterogeneous conductive material is mixed and used in the electrode active material slurry composition of the present invention, reactivity with the active material and the electrolyte is increased, it is easy to form a conductive network in the electrode mixture, and the pore characteristics can be well maintained.

The filler may be selectively used as a component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, and examples thereof include olefin-based polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber may be used. The filler may be included in an amount of 0.1 to 10% by weight based on the total weight of the electrode active material slurry composition.

Meanwhile, the electrode active material slurry composition of the present invention may optionally further include a small amount of a binder in order to improve adhesion between the electrode mixture layer and the electrode current collector.

The binder may include aqueous and non-aqueous binders, and specifically, the aqueous binder is acrylonitrile-butadiene rubber, styrene butadiene rubber (SBR), acrylic rubber, carboxy-modified styrene butadiene rubber, acrylate butadiene A single substance selected from the group consisting of rubber, (meth)acrylic acid alkyl ester, hydroxyethyl cellulose, and a copolymer of carboxymethyl cellulose, or a mixture of two or more thereof may be mentioned.

In addition, the non-aqueous binder is polyvinylidene fluoride (PVDF), acrylonitrile, methacrylonitrile, ethyl acrylonitrile, isopropyl acrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF -co-HFP), polyacrylonitrile, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polyacrylic acid, ethylene-propylene-diene monomer (EPDM), and a single product selected from the group consisting of sulfonated EPDM Or a mixture of two or more of these may be mentioned.

The binder may be included in the range of 0.1 to 5% by weight, specifically 0.1 to 3% by weight, and more specifically 0.1 to 1% by weight, based on the total weight of the electrode active material slurry composition. In this case, by including the binder in an amount of 5% by weight or less, it is possible to implement a more improved resistance reduction effect.

As described above, in the present invention, the non-aqueous additive and the ceramic electrolyte, which are electrolyte components, are included as essential components when preparing the electrode active material slurry, so that ions by the additives after the rolling process for electrode manufacturing or after cell assembly It is possible to secure and control pores (voids) that can serve as a delivery passage. Therefore, it is possible to greatly improve the output characteristics and high rate characteristics of the battery.

In addition, in another embodiment of the present invention

Electrode current collector; And

It provides an electrode for a lithium secondary battery comprising; an electrode mixture layer disposed on at least one surface of the electrode current collector and formed by applying and drying the electrode active material slurry composition of the present invention.

Specifically, as shown in FIG. 1, the electrode for a lithium secondary battery of the present invention includes an electrode active material 3 on at least one surface of the electrode current collector 1; Ion conductive polymer (5); And an electrode mixture layer formed by coating an electrode active material slurry composition including the non-aqueous additive 7 and optionally including the ceramic electrolyte 9, followed by drying and rolling.

The electrode may be an anode or a cathode.

In this case, the electrode current collector may include a positive electrode current collector or a negative electrode current collector according to the type of the electrode.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , Silver, or the like may be used. The positive electrode current collector may generally have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

In addition, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Surface treatment with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. The negative electrode current collector may generally have a thickness of 3 to 500 μm, and, like the positive electrode current collector, microscopic irregularities may be formed on the surface of the current collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

In addition, the electrode active material slurry composition may include at least one of a negative electrode active material slurry composition and a positive electrode active material slurry composition according to the type of the electrode.

In addition, in one embodiment of the present invention,

In a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte,

At least one electrode of the positive electrode or the negative electrode provides a lithium secondary battery including the electrode according to the present invention.

In the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions, and can be used without particular limitation as long as it is used as a separator in a general lithium secondary battery. It is preferable that the resistance is excellent and the electrolytic solution impregnation ability is excellent. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A stacked structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and optionally, a single layer or a multilayer structure may be used.

In addition, electrolytes used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc. that can be used in the manufacture of lithium secondary batteries, limited to these. It does not become.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of a battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, PC), carbonate solvents such as fluoroethylene carbonate (FEC); Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles such as R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, and may contain a double bonded aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolanes or the like may be used. Among them, carbonate-based solvents are preferred, and cyclic carbonates having high ionic conductivity and high dielectric constant (e.g., fluoroethylene carbonate, ethylene carbonate, propylene carbonate, etc.), which can improve the charging/discharging performance of the battery, and low viscosity linear carbonates A mixture of system compounds (eg, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte may exhibit excellent performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ or the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can move effectively.

In addition to the electrolyte constituents, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, and trivalent for the purpose of improving the life characteristics of the battery, suppressing the reduction in battery capacity, and improving the discharge capacity of the battery. Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, or aluminum trichloride may be further included. At this time, the additive may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, portable devices such as mobile phones, notebook computers, and digital cameras, and hybrid electric vehicles (HEVs). ), etc. It is useful in electric vehicle fields.

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack may include a power tool; Electric vehicles including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it may be used as a power source for any one or more medium and large-sized devices among systems for power storage.

Hereinafter, examples will be described in detail to illustrate the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

Example

[Electrode manufacturing]

Example One.

As shown in Table 1 below, 90% by weight of artificial graphite as an anode active material, 3% by weight of Super-P as a conductive material, 2% by weight of PVDF-co-HFP as an ion conductive polymer and 3% by weight of polyethylene oxide, and tetra as a non-aqueous additive. 2% by weight of ethylene glycol dimethyl ether (TEGDME) was mixed with NMP to prepare an anode active material slurry composition having a solid content of 80% by weight.

The negative active material slurry composition was applied to a copper current collector to a thickness of 100 μm, dried at 130° C., and rolled to prepare a negative electrode.

Example 2 and 3.

A negative electrode was prepared in the same manner as in Example 1, except that a negative electrode active material, a conductive material, an ion conductive polymer, a non-aqueous additive, and a ceramic electrolyte were included in an amount as shown in Table 1 below.

Example 4.

As shown in Table 1 below, as a positive electrode active material, Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ 90% by weight, 3% by weight of Super-P as a conductive material, 2% by weight of PVDF-co-HFP as an ion conductive polymer, 3% by weight of polyethylene oxide, and 2% by weight of tetraethylene glycol dimethyl ether (TEGDME) as a non-aqueous additive, with NMP By mixing, a positive electrode active material slurry composition having a solid content of 80% by weight was prepared.

The positive electrode active material slurry composition was applied to an aluminum current collector to a thickness of 120 μm, dried at 130° C., and rolled to prepare a positive electrode.

Example 5 and 6.

A positive electrode was manufactured in the same manner as in Example 4, except that a negative electrode active material, a conductive material, an ion conductive polymer, a non-aqueous additive, and a ceramic electrolyte were included in the amounts shown in Table 1 below.

Example
One Example
2 Example
3 Example
4 Example
5 Example
6 electrode
Active material Artificial graphite 90% by weight 85% by weight 94.8% by weight - - - Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ - - - 90% by weight 85% by weight 94.8% by weight Conductive material Super-P 3% by weight 3% by weight 3% by weight 3% by weight 3% by weight 3% by weight Ion conductive polymer PVDF-co-HFP 2% by weight 2% by weight 1% by weight 2% by weight 1% by weight 1% by weight Polyethylene
Oxide 3% by weight 1% by weight 1% by weight 3% by weight 1% by weight 1% by weight Non-aqueous additive TEGDME 2% by weight 5% by weight 0.1% by weight 2% by weight 5% by weight 0.1% by weight Ceramic electrolyte Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ - 4% by weight 0.1% by weight - 4% by weight 0.1% by weight

Comparative example 1 to 3.

A negative electrode was manufactured in the same manner as in Example 1, except that a negative electrode active material, a conductive material, a binder, an ion conductive polymer, and a non-aqueous additive were included in the amounts shown in Table 2 below.

Comparative example 4 to 6.

As shown in Table 2 below, a positive electrode was manufactured in the same manner as in Example 3, except that a positive electrode active material, a conductive material, an ion conductive polymer, and a non-aqueous additive were included.

Comparative example
One Comparative example
2 Comparative example
3 Comparative example
4 Comparative example
5 Comparative example
6 electrode
Active material Artificial graphite 90
weight% 90
weight% 90% by weight - - - Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ - - - 90
weight% 90
weight% 90
weight% Conductive material Super-P 5
weight% 3.91
weight% 3.9% by weight 5
weight% 3.91
weight% 3.9
weight% Ion conductive polymer PVDF-co-HFP 5
weight% 6% by weight 6
weight% 5
weight% 6% by weight 6% by weight Polyethylene
Oxide - - 0.1
weight% - - 0.1
weight% Non-aqueous additive TEGDME - 0.09
weight% - - 0.09
weight% -

[Manufacture of lithium secondary battery]

Example 7.

An electrode assembly was manufactured by interposing a separator of porous polyethylene between the negative electrode prepared in Example 1 and the positive electrode prepared in Example 4, and after placing the electrode assembly in the case, an electrolyte was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Example 8.

An electrode assembly was prepared by interposing a separator of porous polyethylene between the negative electrode prepared in Example 2 and the positive electrode prepared in Example 5, and after placing the electrode assembly in the case, an electrolyte was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Example 9.

An electrode assembly was manufactured by interposing a separator of porous polyethylene between the negative electrode prepared in Example 3 and the positive electrode prepared in Example 6, and after placing the electrode assembly in the case, an electrolyte was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Comparative example 7.

An electrode assembly was prepared by interposing a separator of porous polyethylene between the negative electrode prepared in Comparative Example 1 and the positive electrode prepared in Comparative Example 4, and after placing the electrode assembly in the case, an electrolyte was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Comparative example 8.

An electrode assembly was manufactured by interposing a separator of porous polyethylene between the negative electrode prepared in Comparative Example 2 and the positive electrode prepared in Comparative Example 5, and after placing the electrode assembly in the case, an electrolyte was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Comparative example 9.

An electrode assembly was manufactured by interposing a separator of porous polyethylene between the negative electrode prepared in Comparative Example 3 and the positive electrode prepared in Comparative Example 6, and after placing the electrode assembly in the case, an electrolyte solution was injected into the case. A lithium secondary battery was prepared. At this time, the electrolyte was prepared by dissolving _{1.0M lithium hexafluorophosphate (LiPF 6} ) in an organic solvent consisting of fluoroethylene carbonate/ethylmethyl carbonate (FEC/EMC mixing volume ratio = 3:7).

Experimental example

Experimental example 1. Internal resistance measurement

[ Was used to measure the electrode resistance. The measured results are shown in the graph of FIG. 2, and the resistance values Rct generated at the interface between the electrode and the electrolyte calculated by measuring the width of the semicircular graph are shown in Table 3 below.

Rct (Ω) Example 7 0.83 Example 8 0.81 Example 9 0.82 Comparative Example 7 0.92 Comparative Example 8 0.90 Comparative Example 9 0.91

As shown in FIG. 2, it can be seen that the semicircle size of the graphs obtained from the secondary batteries of Examples 7 to 9 is smaller than the graphs obtained from the secondary batteries of Comparative Examples 7 to 9. In addition, as shown in Table 3, as a result of checking the interface resistance value of the electrode calculated from the graph, the electrode interface resistance value of the secondary batteries of Examples 7 to 9 is the electrode interface resistance value of the secondary batteries of Examples 7 to 9 It can be seen that it is significantly lower. In particular, it can be seen that the electrode interface resistance values of the secondary batteries of Examples 8 and 9 further including a ceramic electrolyte were lower than the electrode interface resistance values of the secondary battery of Example 7. From these results, it can be predicted that improved rate characteristics and cycle performance can be implemented in the lithium secondary battery of the present invention.

Experimental example 2. Cell resistance measurement

After placing the secondary batteries prepared in Comparative Examples 7 and 9 in a chamber at room temperature (25°C), respectively, in the range of 3 to 4.2 V in a CC/CV (constant current/constant voltage) mode using a charger/discharger. After charging/discharging at 1C/1C condition current continuously 100 cycles, the resistance value (AC-IR, Ω) of the secondary battery was measured with an electric resistance meter (Hioki3554, manufactured by Hioki) at a frequency of 1KHz. The resulting values are shown in Table 4 and FIG. 3 below.

Rcell (Ω) Example 9 0.449 Comparative Example 7 0.473

As shown in Table 4 and FIG. 3, the resistance value (Rcell) of the secondary battery of Example 9 was lower than that of the secondary battery of Comparative Example 7. This result means that the diffusion rate of lithium ions is increased in the secondary battery of Example 9, and it is believed that improved rate characteristics and cycle performance can be exhibited.

1: current collector
3: electrode active material
5: ion conductive polymer
7: non-aqueous additive
9: ceramic electrolyte

Claims (11)

Electrode active material,
Ion conductive polymer including polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer,
Non-aqueous additives,
Ceramic electrolyte, and
Contains a solvent,
The ion conductive polymer is included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition,
The non-aqueous additive includes tetraethylene glycol dimethyl ether,
The ceramic electrolyte is an electrode active material slurry composition containing a phosphate-based material represented by the following formula (1).
[Formula 1]
Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (0<x<1)
The method according to claim 1,
The electrode active material is a positive electrode active material or a negative electrode active material, the electrode active material slurry composition.
delete The method according to claim 1,
The non-aqueous additive is an electrode active material slurry composition that is included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition.
delete delete The method according to claim 1,
The ceramic electrolyte is an electrode active material slurry composition containing lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) _{3 ).}
The method according to claim 1,
The ceramic electrolyte is an electrode active material slurry composition that is included in the range of 0.1% to 5% by weight based on the total weight of the electrode active material slurry composition.
The method according to claim 1,
The solvent is an electrode active material slurry composition containing water or an organic solvent.
Electrode current collector; And
An electrode for a lithium secondary battery comprising; an electrode mixture layer positioned on at least one surface of the electrode current collector and formed by applying and drying the electrode active material slurry composition of claim 1.
In a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte,
At least one electrode of the positive electrode or the negative electrode is a lithium secondary battery comprising the electrode of claim 10.

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