KR20180038764A - Electrode active material slurry composition and secondary battery comprising electrode using the same - Google Patents

Abstract

The present invention relates to electrode active material slurry composition comprising an electrode active material, an ion conductive polymer, a nonaqueous additive, and a ceramic electrolyte, an electrode for a lithium secondary battery including the same, and a lithium secondary battery. In the present invention, the electrode for the lithium secondary battery having reduced internal resistance and improved high-rate characteristics and the lithium secondary battery comprising the same can be manufactured by containing the additive in the manufacture of the electrode slurry composition.

Description

TECHNICAL FIELD [0001] The present invention relates to a lithium secondary battery including an electrode active material slurry composition and an electrode using the electrode active material slurry composition.

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

As technology development and demand for mobile devices are increasing, the demand for secondary batteries as energy sources is rapidly increasing. Among secondary batteries, lithium secondary batteries, which exhibit high energy density and operational potential, have a long cycle life, Have been commercialized and widely used.

Generally, a lithium secondary battery includes a positive electrode and a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution in which a lithium salt is dissolved in an organic solvent. The positive electrode and the negative electrode each have an electrode active material , Followed by drying and pressing.

On the other hand, in order to maximize the thickness uniformity of the electrode material mixture layer and the energy density in the electrode as the need for a high-capacity battery increases, the active material particles are broken or the electrode material mixture layer There is a problem that the compression is intensified and the ratio of the pores inside the electrode compound mixture layer is decreased.

When the porosity ratio is decreased as described above, it is difficult to impregnate the electrolytic solution into the inside of the electrode, so that it is difficult to secure an ion movement path and ion conductivity is lowered. As a result, the rate characteristic of the battery is reduced, resulting in deterioration of battery performance and lifetime characteristics.

Accordingly, it is an object of the present invention to provide an electrode structure capable of achieving an effective adhesion performance between the electrode current collector and the electrode mixture layer while increasing capacity characteristics of the battery for increasing the density of the electrode and securing an ion movement path inside the electrode mixture layer after the rolling process .

Korean Patent Publication No. 10-2016-0038080

In order to solve the above problems,

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

A second object of the present invention is to provide an electrode for a lithium secondary battery manufactured using the electrode active material slurry composition.

A third object of the present invention is to provide a lithium secondary battery having the electrode for the lithium secondary battery.

Specifically, in one embodiment of the present invention

Electrode active material;

An ion conductive polymer comprising polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP);

Non-aqueous additives; And

A solvent;

Wherein the ion conductive polymer is contained in an amount of 0.1 wt% to 5 wt% 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 contained in an amount of 0.1 wt% to 5 wt% 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 be a phosphate-based material represented by the following formula (1).

[Chemical Formula 1]

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

Specifically, the ceramic electrolyte may be lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ; LAGP), and may be in the range of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition &Lt; / RTI &gt;

In an embodiment of the present invention,

Electrode collector; And

And an electrode mixture layer formed on at least one surface of the current collector and formed by coating and drying the electrode active material slurry composition of the present invention.

At this time, the electrode may be an anode or a cathode.

In an embodiment of the present invention,

1. 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,

And at least one of the positive electrode and the negative electrode includes the electrode according to the present invention.

In the present invention, an additive capable of acting as an ion transfer passage for securing the adhesion between the electrode active material or between the electrode mixture and the electrode current collector during the preparation of the electrode slurry composition is included, thereby reducing the internal resistance and improving the high- Electrode and a lithium secondary battery having the electrode 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.
FIG. 2 is a graph showing the results of measurement of internal interface resistance characteristics of the secondary batteries of Examples 7 to 9 and Comparative Examples 7 to 9. FIG.
3 is a graph showing the results of measurement of resistance characteristics of the secondary battery cells of Example 9 and Comparative Example 7. FIG.

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

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Conventionally, an electrode for a secondary battery is manufactured by preparing an electrode active material slurry, applying it on an electrode current collector, drying and rolling. At this time, if the high pressure is applied in order to increase the filling density of the electrode in the rolling process, the pressure inside the electrode active material mixture layer is increased, and the pore ratio in the electrode material mixture layer is reduced. As a result, it is difficult to impregnate the electrolyte into the inside of the electrode, so that the ion transfer path can not be secured, and ion conductivity is lowered, resulting in a decrease in the rate characteristic.

Therefore, in the present invention, the electrolyte used for the gel polymer electrolyte in the preparation of the electrode active material slurry composition is further included as an additive, so that it is possible to maintain and secure the pores in the electrode mixture layer even after the rolling process, An electrode for a secondary battery and a lithium secondary battery having the electrode can be manufactured.

Specifically, in one embodiment of the present invention

Electrode active material;

An ion conductive polymer comprising polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP);

Non-aqueous additives; And

A solvent;

Wherein the ion conductive polymer is contained in an amount of 0.1 wt% to 5 wt% 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.

Therefore, the electrode active material slurry may include at least one of a cathode active material and a negative active material depending on the kind of the electrode active material slurry composition.

The cathode active material is a compound capable of reversibly intercalating and deintercalating lithium, and may specifically include a lithium composite metal oxide including lithium and at least one metal such as cobalt, manganese, nickel, or aluminum have.

More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (for example, LiMnO ₂ , LiMn ₂ O ₄ And the like), lithium-cobalt oxide (e.g., LiCoO ₂ and the like), lithium-nickel-based oxide (for example, LiNiO ₂ and the like), lithium-nickel-manganese-based oxide (for example, 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) and the like), 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) and the like), lithium-nickel-manganese-cobalt oxide (e.g., 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, P2, Q2, R2 and S2 are independently (0 <P2 <1, 0 <Q2 <1, 0 <R2 <1, 0 <S2 <1, P2 + Q2 + R2 + S2 = 1) Any one or two or more of these compounds may be included. The lithium composite metal oxide may be LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , 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 that the remarkable effect of improvement of 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 . 1} O _2, etc., and any one or a mixture of two or more thereof may be used.

At least one of the metal elements other than lithium in the lithium composite metal oxide is selected from the group consisting of W, MoZr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, But may be doped by any one or two or more elements. When the lithium composite metal oxide of lithium deficiency is further doped with the metal element, the structural stability of the cathode active material is improved, and as a result, the output characteristics of the battery can be improved. At this time, the content of the doping element contained in the lithium composite metal oxide may be appropriately controlled within a range not to deteriorate the characteristics of the cathode active material, and may be 0.02 atomic% or less.

The negative electrode active material is a compound capable of reversibly intercalating and deintercalating 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 alloys, Sn alloys or Al alloys; Metal oxides capable of doping and dedoping lithium such as SiO _{x 1} (0 <x 1 <2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Or a composite containing the metallic compound and the carbonaceous material such as Si-C composite or Sn-C composite, and any one or a mixture of two or more thereof may be used. Also, a metal lithium thin film may be used as the negative electrode active material. The carbon material may be both low-crystalline carbon and high-crystallinity carbon. Examples of the low-crystalline carbon include soft carbon and hard carbon. Examples of the highly crystalline carbon include natural graphite, artificial graphite, artificial graphite or artificial graphite, Kish graphite graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitches. derived cokes).

The electrode active material may include 80 to 99% by weight based on the total weight of the electrode active material slurry composition. When the content of the electrode active material is less than 80 wt%, the capacity characteristics of the battery are deteriorated. When the content of the electrode active material is more than 99 wt%, the contact ratio between the electrode active material and the conductive material decreases, The output characteristics of the battery may be deteriorated.

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) capable of simultaneously performing a binder function .

The ion conductive polymer may be contained in an amount of 0.1 wt% to 5 wt% 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 wt%, there may occur disadvantages such as separation of the electrode active material layer due to reduction of the adhesion force between the electrode active material and the electrode current collector. If the content is more than 5 wt% The output characteristics of the battery may be degraded due to a decrease in the content of the electrode active material.

Further, 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 transfer path.

The non-aqueous additive may be added in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition. 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 be deteriorated. If the content of the non-aqueous additive is more than 5% by weight, The output characteristics of the 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 the following formula (1).

[Chemical Formula 1]

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

Specifically, the ceramic electrolyte may be lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ; LAGP), and may be in the range of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition &Lt; / RTI &gt;

If the content of the ceramic electrolyte is less than 0.1 wt%, the effect of securing the ion transport path is insufficient. If the content of the ceramic electrolyte is more than 5 wt%, the resistance is increased, .

In the electrode active material slurry composition of the present invention, the solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), and the electrode active material, the ion conductive polymer, So as to have a preferable viscosity depending on the type of the ceramic electrolyte. For example, the concentration of the solid content including the electrode active material, the ion conductive polymer, the non-aqueous additive, and optionally the ceramic electrolyte may be 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

In the case of using an excessive amount of binder for securing the adhesive force at the time of preparing the electrode active material slurry, not only the ratio of the electrode active material is reduced but also the function of the binder itself decreases as the resistance element acts in the electrode, . Further, there is a problem that the mixing time is prolonged and the process efficiency is lowered, and there is a problem that the capacity decrease and the cell resistance increase at the high temperature storage are accelerated due to the side reaction with the electrolyte solution. However, when the binder content is reduced, it is difficult to secure the adhesion between the electrode current collector and the electrode assembly layer, thereby causing the electrode peeling phenomenon 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 an external impact, which has a disadvantage that adversely affects stability such as lifetime characteristics of the battery.

In the present invention, when an electrode active material slurry composition is prepared, an ion conductive polymer capable of acting as a binder, a non-aqueous additive capable of acting as an ion transmission path, and a ceramic electrolyte are included, thereby securing the adhesive force between the electrode active material and the electrode collector In addition to this, it is possible to achieve the effect of securing the ion movement path and reducing the resistance of the electrode interface after the rolling process.

In addition, the electrode active material slurry composition of the present invention may 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 in the battery. The conductive material may further include different kinds of conductive materials having different shapes such as a particle shape, a fibrous shape or a plate shape. May be contained in an amount of 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 any particular limitation as long as it has conductivity and satisfies its morphological conditions. However, considering that the improvement effect of use of the particulate conductive material is excellent, the particulate conductive material may be natural graphite or artificial graphite Graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, or denka black, and either one or a mixture of two or more of them may be used.

When the conductive material is a particulate conductive material, specifically, it may have an average particle diameter (D ₅₀ ) of 10 to 45 nm and a specific surface area of 40 to 170 m ² / g. If the average particle diameter of the particulate conductive material is less than 10 nm, or if the specific surface area exceeds 170 m ² / g, the dispersibility in the positive electrode mixture significantly decreases due to agglomeration of the particulate conductive materials, and if the average particle diameter exceeds 45 nm, If the surface area is as large as 40 m ² / g, the size of the anode active material is too large, so that the anode active material may not be uniformly dispersed throughout the anode mixture in the conductive material arrangement according to the porosity of the cathode active material.

The fibrous or plate-like conductive material is a conductive material having two planes corresponding to each other and having an aggregate structure having a horizontal size larger than that of a vertical direction. The conductive material has a flake ), Scales, and the like. As the fibrous or plate-shaped conductive material, conductive fibers such as carbon fiber and metal fiber may be used.

In addition, the conductive material may be a metal powder such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

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

The filler may be selectively used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber, carbon fiber and the like can 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 binder to improve adhesion between the electrode mixture layer and the electrode current collector.

The binder may include an aqueous binder and a non-aqueous binder. Specifically, the aqueous binder may include acrylonitrile-butadiene rubber, styrene butadiene rubber (SBR), acrylic rubber, carboxy modified styrene butadiene rubber, acrylate butadiene rubber Rubber, a (meth) acrylic acid alkyl ester, a copolymer of hydroxyethyl cellulose and carboxymethyl cellulose, or a mixture of two or more thereof.

Also, the non-aqueous binder may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), acrylonitrile, methacrylonitrile, ethyl acrylonitrile, isopropyl acrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymer -CO-HFP), a single substance selected from the group consisting of polyacrylonitrile, polyvinylpyrrolidone, polytetrafluoroethylene (PTFE), polyacrylic acid, ethylene-propylene-diene monomer (EPDM), and sulfonated EPDM Or a mixture of two or more of them.

The binder may be contained in an amount of 0.1 to 5% by weight, specifically 0.1 to 3% by weight, more specifically 0.1 to 1% by weight based on the total weight of the electrode active material slurry composition. At this time, by including the binder in an amount of 5 wt% or less, a further improved resistance reduction effect can be realized.

As described above, in the present invention, the nonaqueous additive and the ceramic electrolyte, which are electrolyte components, are included as essential components in the preparation of the slurry of the electrode active material, so that after the rolling process for preparing the electrode or after the cell assembly, It is possible to secure and control pores (air gaps) that can serve as transmission passages. Therefore, the output characteristics and the high-rate characteristics of the battery can be greatly improved.

In another embodiment of the present invention,

Electrode collector; And

And an electrode mixture layer formed on at least one surface of the current collector and formed by coating 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 comprises an electrode active material 3 on at least one surface of an electrode current collector 1; An ion conductive polymer (5); And a non-aqueous additive (7), and optionally an electrode active material slurry composition comprising a ceramic electrolyte (9), followed by drying and rolling.

The electrode may be an anode or a cathode.

At this time, depending on the type of the electrode, the electrode current collector may include a positive electrode collector or a negative electrode collector.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, carbon, nickel, titanium, , Silver or the like may be used. The cathode current collector may have a thickness of usually 3 to 500 탆 and fine irregularities may be formed on the surface of the current collector to increase the adhesive force of the cathode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like can be used. The negative electrode current collector may have a thickness of 3 to 500 탆, and like the positive electrode current collector, fine unevenness may be formed on the current collector surface to enhance the binding force of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

In addition, the electrode active material slurry composition may include at least one of the negative electrode active material slurry composition and the positive electrode active material slurry composition of the present invention, depending on the type of the electrode.

Further, in an embodiment of the present invention,

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,

And at least one of the positive electrode and the negative electrode includes 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 moving path of lithium ions. The separator can be used without limitation, as long as it is used as a separator in a lithium secondary battery. Particularly, It is preferable that it is a resistance and excellent in an electrolyte impregnation ability. Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used. In order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may be optionally used as a single layer or a multilayer structure.

Examples of the electrolyte used in the present invention include an organic-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte which can be used in the production of a lithium secondary battery. It is not.

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

The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC), fluoroethylene carbonate (FEC), etc .; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; R-CN (R is a straight, branched or cyclic hydrocarbon group of C2 to C20, which may contain a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Of these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., fluoroethylene carbonate, ethylene carbonate, or propylene carbonate) having a high ionic conductivity and high dielectric constant capable of increasing the charge- And a mixture of a base compound (for example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) 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 performance of the electrolytic solution may be excellent.

The lithium salt can 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, 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 may be used. The concentration of the lithium salt is preferably in the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has an appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and the lithium ion can effectively move.

In addition to the electrolyte components, the electrolyte may contain, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate or the like, pyridine, triethanolamine, or the like for the purpose of improving lifetime characteristics of the battery, Ethyl phosphite, triethanol amine, cyclic ether, ethylenediamine, glyme, hexametriamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, At least one additive such as benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, benzyl alcohol, 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 rate, it can be applied to portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles ) And the like.

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

Hereinafter, the present invention will be described in detail by way of examples with reference to the following examples. However, the embodiments according to the present invention can be modified into 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 enable those skilled in the art to more fully understand the present invention.

Example

[Electrode Fabrication]

Example  One.

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

The anode active material slurry composition was applied to a copper collector to a thickness of 100 탆, dried at 130 캜, 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 the negative electrode active material, the conductive material, the ion conductive polymer, the non-aqueous additive and the ceramic electrolyte were contained in the amounts shown in Table 1 below.

Example  4.

As shown in the following Table 1, Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ 3% by weight of polyethylene oxide, and 2% by weight of tetraethylene glycol dimethyl ether (TEGDME), which is a non-aqueous additive, were mixed with NMP To prepare a cathode active material slurry composition having a solid content of 80% by weight.

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

Example  5 and 6.

A positive electrode was prepared in the same manner as in Example 4 except that the negative electrode active material, the conductive material, the ion conductive polymer, the non-aqueous additive, and the ceramic electrolyte were contained 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 wt% 85 wt% 94.8 wt% - - - Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ - - - 90 wt% 85 wt% 94.8 wt% Conductive material Super-P 3 wt% 3 wt% 3 wt% 3 wt% 3 wt% 3 wt% Ion conductive polymer PVDF-co-HFP 2 wt% 2 wt% 1 wt% 2 wt% 1 wt% 1 wt% Polyethylene
Oxide 3 wt% 1 wt% 1 wt% 3 wt% 1 wt% 1 wt% Non-aqueous additive TEGDME 2 wt% 5 wt% 0.1 wt% 2 wt% 5 wt% 0.1 wt% Ceramic electrolyte Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ - 4 wt% 0.1 wt% - 4 wt% 0.1 wt%

Comparative Example  1-3.

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

Comparative Example  4 to 6.

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

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 wt% - - - 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 wt% 5
weight% 3.91
weight% 3.9
weight% Ion conductive polymer PVDF-co-HFP 5
weight% 6 wt% 6
weight% 5
weight% 6 wt% 6 wt% Polyethylene
Oxide - - 0.1
weight% - - 0.1
weight% Non-aqueous additive TEGDME - 0.09
weight% - - 0.09
weight% -

[Production of lithium secondary battery]

Example  7.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Example 1 and the positive electrode prepared in Example 4, and the electrode assembly was placed in the case, and then an electrolyte solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Example  8.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Example 2 and the positive electrode prepared in Example 5, and the electrode assembly was placed inside the case, and then an electrolytic solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Example  9.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Example 3 and the positive electrode prepared in Example 6, and the electrode assembly was placed in the case, and then an electrolytic solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Comparative Example  7.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Comparative Example 1 and the positive electrode prepared in Comparative Example 4, the electrode assembly was placed inside the case, and an electrolyte solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Comparative Example  8.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Comparative Example 2 and the positive electrode prepared in Comparative Example 5, the electrode assembly was placed inside the case, and an electrolyte solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Comparative Example  9.

An electrode assembly was manufactured through a separator made of porous polyethylene between the negative electrode prepared in Comparative Example 3 and the positive electrode prepared in Comparative Example 6, the electrode assembly was placed inside the case, and an electrolyte solution was injected into the case Thereby preparing a lithium secondary battery. The electrolyte solution was prepared by dissolving 1.0 M lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent composed of fluoroethylene carbonate / ethylmethyl carbonate (FEC / EMC mixing ratio = 3: 7).

Experimental Example

Experimental Example  1. Internal resistance measurement

Electrochemical impedance spectroscopy (EIS) was performed at 75,300 Hz, 300 Hz and 2.5 Hz after one charge-discharge cycle of the secondary batteries of Examples 7 to 9 and Comparative Examples 7 to 9 at room temperature (25 ° C) To measure the electrode resistance. The measured results are shown in the graph of FIG. 2, and the resistance value (Rct) generated at the interface between the electrode and the electrolyte calculated by measuring the width of the semicircle graph is 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 semi-circle size of the graph obtained from the secondary batteries of Examples 7 to 9 is smaller than the graph obtained from the secondary batteries of Comparative Examples 7 to 9. Also, as shown in Table 3, the interfacial resistance values of the electrodes calculated from the graph were checked. As a result, the electrode interfacial resistance values of the secondary batteries of Examples 7 to 9 were compared with the electrode interfacial resistance values 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, which further include the ceramic electrolyte, are lower than the electrode interface resistance value of the secondary battery of Example 7. [ From these results, it can be predicted that an improved rate characteristic and cycle performance can be realized in the lithium secondary battery of the present invention.

Experimental Example  2. Cell resistance measurement

The secondary batteries prepared in Comparative Example 7 and Example 9 were placed in a chamber at room temperature (25 ° C), respectively, and charged in a constant current / constant voltage (CC / CV) mode in the range of 3 to 4.2 V The resistance (AC-IR,?) Of the secondary battery was measured with an electric resistance meter (Hioki 3554, Hioki Co., Ltd.) at a frequency of 1 KHz after charging and discharging were continuously carried out with a current of 1 C / The results are shown in Table 4 and FIG.

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 the resistance value of the secondary battery of Comparative Example 7. These results indicate that the diffusion rate of lithium ion increases in the secondary battery of Example 9, and thus it is considered that the improved rate characteristics and cycle performance can be exhibited.

1: Home
3: electrode active material
5: ion conductive polymer
7: Non-aqueous additive
9: Ceramic electrolyte

Claims (11)

Electrode active material,
An ion conductive polymer including polyethylene oxide and vinylidene fluoride-hexafluoropropylene copolymer,
Non-aqueous additives, and
A solvent,
Wherein the ion conductive polymer is contained in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition.
The method according to claim 1,
Wherein the electrode active material is a positive electrode active material or a negative electrode active material.
The method according to claim 1,
Wherein the non-aqueous additive is tetraethylene glycol dimethyl ether.
The method according to claim 1,
Wherein the non-aqueous additive is contained in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition.
The method according to claim 1,
Wherein the electrode active material slurry composition further comprises a ceramic electrolyte.
The method of claim 5,
Wherein the ceramic electrolyte comprises a phosphate-based material represented by the following formula (1).
[Chemical Formula 1]
Li _{1 + x} Al _x Ge _{2 - x} (PO ₄ ) ₃ (0 <x <1)
The method of claim 5,
Wherein the ceramic electrolyte comprises lithium aluminum germanium phosphate (Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ ).
The method of claim 5,
Wherein the ceramic electrolyte is contained in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrode active material slurry composition.
The method according to claim 1,
Wherein the solvent comprises water or an organic solvent.
Electrode collector; And
And an electrode material mixture layer formed on at least one surface of the electrode current collector and formed by coating and drying the electrode active material slurry composition according to claim 1.
1. 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,
And at least one of the positive electrode and the negative electrode includes the electrode of claim 10.

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