KR102134016B1 - Electrode and electrochemical device including the same - Google Patents

Abstract

The present invention relates to an electrode capable of reducing the resistance by improving the adhesive strength of the electrode and reducing the amount of unnecessary binder, and an electrochemical device comprising the same. According to the present invention, the electrode current collector; It is formed on one or both sides of the electrode current collector, an electrode active material layer comprising an electrode active material, a first polymer binder containing polyvinylidene fluoride, and a conductive material; includes, the electrode active material layer is chlorotrifluor A second polymer binder comprising a copolymer of roethylene and polyvinylidene fluoride, a copolymer of hexafluoropropylene and polyvinylidene fluoride, or a mixture thereof, based on 100 parts by weight of the first polymer binder, 20 to 80 weight An electrode characterized in that it further comprises a negative is provided.

Description

Electrode and electrochemical device including the same}

The present invention relates to an electrode and an electrochemical device comprising the same, and more particularly, to an electrode having improved adhesion of the electrode and an electrochemical device comprising the same.

Recently, interest in energy storage technology has been increasing. As the field of application extends to the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts for research and development of electrochemical devices are becoming more concrete. The electrochemical device is the area that is receiving the most attention in this aspect, and among them, the development of a rechargeable battery that can be charged and discharged has become a focus of interest, and recently, in developing such a battery, in order to improve capacity density and specific energy, a new Research and development are being conducted on the design of electrodes and batteries.

Among the currently applied secondary batteries, lithium secondary batteries developed in the early 1990s have the advantage of higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries using aqueous electrolyte solutions. Is in the limelight.

On the other hand, the electrode used in the electrochemical device is prepared by applying an electrode active material slurry containing an electrode active material and a binder to at least one surface of the electrode current collector, followed by drying. The electrode active material may have a volume expansion according to charge and discharge, and the adhesive strength of the binder is weak, so it is easy to lose the conductive structure, and there is a problem of deteriorating the life characteristics of the electrochemical device.

Accordingly, a problem to be solved by the present invention is to provide an electrode and an electrochemical device including the same, which can improve the adhesion of the electrode to achieve an output improvement of the electrochemical device.

In order to solve the above problems, according to an aspect of the present invention, the electrode current collector; It is formed on one or both sides of the electrode current collector, an electrode active material layer comprising an electrode active material, a first polymer binder containing polyvinylidene fluoride, and a conductive material; includes, the electrode active material layer is chlorotrifluor A second polymer binder comprising a copolymer of roethylene and polyvinylidene fluoride, a copolymer of hexafluoropropylene and polyvinylidene fluoride, or a mixture thereof, based on 100 parts by weight of the first polymer binder, 20 to 80 weight An electrode characterized in that it further comprises a negative is provided.

Preferably, the adhesive force of the electrode may be 100 gf/cm or more.

Preferably, the weight average molecular weight of the first polymer binder is 200,000 to 1,300,000, and the weight average molecular weight of the second polymer binder may be 400,000 to 1,000,000.

Preferably, the second polymer binder may include a copolymer of chlorotrifluoroethylene and polyvinylidene fluoride and a copolymer of hexafluoropropylene and polyvinylidene fluoride in a weight ratio of 30:70 to 70:30. have.

Preferably, the content of chlorotrifluoroethylene of the copolymer of chlorotrifluoroethylene and polyvinylidene fluoride is 5 to 70% by weight, and hexafluoro of the copolymer of hexafluoropropylene and polyvinylidene fluoride. The content of propylene may be 5 to 70% by weight.

Preferably, the melting point of the first polymer binder may be 100 to 200°C, and the melting point of the second polymer binder may be 100 to 220°C.

Preferably, the electrode may be an anode or a cathode.

Preferably, the electrode active layer may be made of a result of drying the slurry for the electrode.

The drying step may include a first drying step performed at a temperature of 120 to 140°C, and a second drying step performed at a vacuum of 80 to 100°C.

In addition, according to an aspect of the present invention, in an electrochemical device including an anode, a cathode, a separator interposed between the anode and the cathode, and a non-aqueous electrolyte, the anode and the cathode are provided with an electrochemical device that is the above-described electrode. .

Preferably, the electrochemical device may be a lithium secondary battery.

According to an embodiment of the present invention, it is possible to improve the adhesion of the electrode and to reduce the content of the binder, thereby improving the output of the electrochemical device.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms or words used in the specification and claims should not be interpreted as being limited to ordinary or dictionary meanings, and the inventor can appropriately define the concept of terms in order to best describe his or her invention. Based on the principle of being present, it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

Accordingly, the embodiments described in the present specification and the configurations described in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, and thus can replace them at the time of application. It should be understood that there may be equivalents and variations.

The electrode according to the present invention includes an electrode current collector; It is formed on one or both sides of the electrode current collector, an electrode active material layer comprising an electrode active material, a first polymer binder containing polyvinylidene fluoride, and a conductive material; includes, the electrode active material layer is chlorotrifluor A second polymer binder comprising a copolymer of roethylene and polyvinylidene fluoride, a copolymer of hexafluoropropylene and polyvinylidene fluoride, or a mixture thereof, based on 100 parts by weight of the first polymer binder, 20 to 80 weight Includes more as wealth.

The polymer binder (first polymer binder, second polymer binder) may be included in 5 to 10 parts by weight based on 100 parts by weight of the electrode active material layer.

Polyvinylidene fluoride was used as a polymer binder for a conventional electrode active material layer, but the present invention is a copolymer of chlorotrifluoroethylene and polyvinylidene fluoride, a copolymer of hexafluoropropylene and polyvinylidene fluoride, or a mixture thereof. By further comprising a second polymer binder comprising a, it is possible to improve the adhesion of the electrode compared to the prior art.

The electrode active material layer may have an adhesive strength of 100 gf/cm or more.

The weight average molecular weight of the first polymer binder is 200,000 to 1,300,000, and the weight average molecular weight of the second polymer binder may be 400,000 to 1,000,000.

When the second polymer binder includes both a copolymer of chlorotrifluoroethylene and polyvinylidene fluoride and a copolymer of hexafluoropropylene and polyvinylidene fluoride, these are included in a ratio of 30:70 to 70:30 can do.

The content of chlorotrifluoroethylene of the copolymer of chlorotrifluoroethylene and polyvinylidene fluoride is 5 to 70% by weight, and the content of hexafluoropropylene of the copolymer of hexafluoropropylene and polyvinylidene fluoride is It may be 5 to 70% by weight.

The first polymer binder may have a melting point of 100 to 200°C, and the second polymer binder may have a melting point of 100 to 220°C.

According to an embodiment of the present invention, the electrode is a positive electrode, and the electrode active material is a positive electrode active material, and may be a lithium-containing oxide. As the lithium-containing oxide, a lithium-containing transition metal oxide can be preferably used. For example, the lithium-containing transition metal oxide is Li _x CoO ₂ (0.5<x<1.3), Li _x NiO ₂ (0.5<x<1.3), Li _x MnO ₂ (0.5<x<1.3), Li _x Mn ₂ O ₄ (0.5<x<1.3), Li _x (Ni _a Co _b Mn _c )O ₂ (0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, a +b+c=1), Li _x Ni _1-y Co _y O ₂ (0.5<x<1.3, 0<y<1), Li _x Co _{1 - y} Mn _y O ₂ (0.5<x<1.3, 0 ≤y<1), Li _x Ni _{1 -y} Mn _y O ₂ (0.5<x<1.3, O≤y<1), Li _x (Ni _a Co _b Mn _c )O ₄ (0.5<x<1.3, 0 <a<2, 0<b<2, 0<c<2, a+b+c=2), Li _x Mn _{2 - z} Ni _z O ₄ (0.5<x<1.3, 0<z<2), Group consisting of Li _x Mn _{2 - z} Co _z O ₄ (0.5<x<1.3, 0<z<2), Li _x CoPO ₄ (0.5<x<1.3) and Li _x FePO ₄ (0.5<x<1.3) It may be any one selected from or a mixture of two or more of them, and the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). In addition, sulfide, selenide and halide may be used in addition to the lithium-containing transition metal oxide.

According to an embodiment of the present invention, the electrode is a negative electrode, and the electrode active material may be any one selected from the group consisting of lithium metal, carbon materials, and metal compounds, or a mixture of two or more of them.

Specifically, both low-crystalline carbon and high-crystalline carbon may be used as the carbon material. Soft carbon and hard carbon are typical examples of low crystalline carbon, and natural graphite, Kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fibers are typical of high crystalline carbon. High-temperature calcined carbons such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes are typical examples.

The metal compounds include metal elements such as Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, Sr, Ba And compounds containing at least one of them. These metal compounds are simple substance, alloy, oxide (TiO ₂ , SnO ₂ Etc.), nitrides, sulfides, borides, alloys with lithium, etc. can be used in any form, but simple substances, alloys, oxides, alloys with lithium can be increased in capacity. Among them, one or more elements selected from Si, Ge and Sn can be contained, and one or more elements selected from Si and Sn can further increase the capacity of the battery.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the electrochemical device. As the conductive material, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, etc. may be used. As a commercially available product, acetylene black series (Chevron) Chemical Company (Chevron Chemical Company or Gulf Oil Company, etc.), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cavott) Company (product of Cabot Company) and Super P (product of MMM). Examples include acetylene black, carbon black, and graphite.

The electrode current collector is a metal having high conductivity and can be used as long as it is a metal to which the electrode active material slurry can be easily adhered and is not reactive in the voltage range of the electrochemical device. Specifically, a non-limiting example of a current collector for a positive electrode includes aluminum, nickel, or a foil produced by a combination thereof, and a non-limiting example of a current collector for a negative electrode is copper, gold, nickel, or a copper alloy or a combination thereof. And the like manufactured by foil. In addition, the current collector may be used by laminating substrates made of the materials.

The electrode active material layer may be formed as a result of drying the slurry for the electrode. It can be prepared by kneading using an electrode active material, a conductive material, a binder, and a dispersion medium to prepare an electrode active material slurry, and then applying it to a current collector, followed by a drying step. The drying step is not particularly limited, and may be performed at steps 1 to 8, at a temperature of 80 to 140° C., for example, a first drying step performed at a temperature of 120 to 140° C., and 80 to 100° C. It may be manufactured through a second drying step performed in a vacuum state.

The dispersion medium, acetone (acetone), tetra hydrofuran (tetra hydrofuran), methylene chloride (methylene chloride), chloroform (chloroform), dimethylform amide (dimethylform amide), N-methyl-2-pyrrolidone (N-methyl It may be any one selected from the group consisting of -2-pyrrolidone, NMP), cyclohexane and water, or a mixture of two or more of them.

In addition, according to an embodiment of the present invention, an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode; A non-aqueous electrolyte that impregnates the electrode assembly; And a battery case incorporating the electrode assembly and the non-aqueous electrolyte, wherein at least one of the positive electrode and the negative electrode is provided with an electrochemical device that is an electrode of the present invention.

The separator according to the present invention may be used as long as it is a porous substrate used in an electrochemical device, and for example, a polyolefin-based porous membrane or a nonwoven fabric may be used, but is not particularly limited thereto.

Examples of the polyolefin-based porous membrane include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high-molecular-weight polyethylene, respectively, or formed of polymers of these. One membrane is mentioned.

The nonwoven fabric includes, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalene, etc. individually or And nonwoven fabrics formed of polymers in which these are mixed. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a melt blown nonwoven fabric.

The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and pores present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

On the other hand, in order to improve the mechanical strength of the separator made of the porous substrate and suppress the short circuit between the positive electrode and the negative electrode, a porous coating layer including inorganic particles and a polymer binder may be further included on at least one surface of the porous substrate.

In the porous coating layer, the polymer binder attaches them to each other so that the inorganic particles can be bound to each other (ie, the polymer binder is connected and fixed between the inorganic particles), and the porous coating layer is bound to the porous substrate by the polymer binder. Remain intact. The inorganic particles of the porous coating layer are present in a close-packed structure with substantially contacting each other, and the interstitial volume generated when the inorganic particles are contacted becomes pores of the porous coating layer.

In this case, the inorganic particles used are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles are not particularly limited as long as they do not undergo oxidation and/or reduction reactions in the operating voltage range of the applied electrochemical device (eg, 0 to 5 V based on Li/Li ⁺ ). Particularly, when using inorganic particles having ion transport ability, performance can be improved by increasing ion conductivity in an electrochemical device.

In addition, when inorganic particles having a high dielectric constant are used as the inorganic particles, ionic conductivity of the electrolyte may be improved by contributing to an increase in dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte.

For the aforementioned reasons, the inorganic particles may include high dielectric constant inorganic particles having a dielectric constant of 5 or higher, or 10 or higher, inorganic particles having lithium ion transfer ability, or mixtures thereof.

Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb(Zr _x Ti _1-x )O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where 0 <x <1, 0 <y <1), (1-x)Pb(Mg _1/3 Nb _2/3 )O ₃ -xPbTiO ₃ (PMN-PT, where 0 < x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ Etc. can be used individually or in mixture of 2 or more types, respectively.

In particular, the aforementioned BaTiO ₃ , Pb(Zr _x Ti _1-x )O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where 0 < x <1, 0 <y <1), (1-x)Pb(Mg _1/3 Nb _2/3 )O _{3 - x} PbTiO ₃ (PMN-PT, where 0 <x <1), hafnia ( Inorganic particles such as HfO ₂ ) not only exhibit high dielectric constant characteristics with a dielectric constant of 100 or more, but also generate piezoelectricity when they are tensioned or compressed by applying a certain pressure, and thus have a piezoelectricity that causes a potential difference between both sides. It is possible to improve the safety of the electrochemical device by preventing the occurrence of an internal short circuit of the positive electrode due to impact. In addition, when the above-mentioned high dielectric constant inorganic particles and inorganic particles having lithium ion transfer ability are mixed, their synergistic effect may be doubled.

The inorganic particle having the lithium ion transfer ability refers to an inorganic particle having a function of transferring lithium ions without storing lithium but containing lithium elements, and the inorganic particle having a lithium ion transfer ability exists inside the particle structure Since lithium ions can be transferred and moved due to a kind of defect, lithium ion conductivity in the battery is improved, thereby improving battery performance. Non-limiting examples of the inorganic particles having the lithium ion transfer ability is lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3) , Lithium aluminum titanium phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P (LiAlTiP) _x O _y series glass such as ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanitanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3 ), Li _{3 . 25} Ge _{0 .25} P _{0. 75} S ₄ Lithium germanium thiophosphate (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), lithium nitride such as Li ₃ N SiS ₂ series glass (Li _x Si _y S _z , 0 <x <3) such as ride (Li _x N _y , 0 <x <4, 0 <y <2), Li ₃ PO ₄ -Li ₂ S-SiS ₂ , 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based glass _{(Li x P y S z,} 0 <x <3, 0 <y <3, 0 <z <7) or mixtures thereof.

Further, as the polymer binder used for forming the porous coating layer, a polymer commonly used for forming a porous coating layer in the art may be used.

Non-limiting examples of such a polymeric binder include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, poly Methyl methacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co- vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulose And cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose. have.

In addition, the weight ratio of the inorganic particles and the polymer binder may be 50:50 to 99:1, or 60:40 to 90:10, or 70:30 to 80:20.

In addition, the thickness of the porous coating layer composed of inorganic particles and a polymer binder is not particularly limited, but may be in the range of 0.01 to 20 μm. In addition, the pore size and porosity are also not particularly limited, but the pore size may range from 0.01 to 10 μm, and the porosity may range from 5 to 90%.

Meanwhile, the non-aqueous electrolyte solution may include an organic solvent and an electrolyte salt, and the electrolyte salt is a lithium salt. The lithium salt may be used without limitation those commonly used in the non-aqueous electrolyte for lithium secondary batteries. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( ^{_{CF 3 SO 2) 3 C -}} , CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may include any one or two or more selected from the group consisting of.

And, as the organic solvent contained in the above-mentioned non-aqueous electrolyte solution, those commonly used in the non-aqueous electrolyte solution for lithium secondary batteries can be used without limitation, for example, ether, ester, amide, linear carbonate, cyclic carbonate, etc., respectively, alone or It can be used by mixing two or more kinds.

Among them, a carbonate compound which is representatively a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, and 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and any one selected from the group consisting of halides, or mixtures of two or more of them. Examples of these halides include, but are not limited to, fluoroethylene carbonate (FEC).

In addition, specific examples of the linear carbonate compound may be selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate, or Among them, a mixture of two or more kinds may be representatively used, but is not limited thereto.

Particularly, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents and have a high dielectric constant, so that lithium salts in the electrolyte can be better dissociated, such as dimethyl carbonate and diethyl carbonate. When a low-viscosity, low-permittivity linear carbonate is mixed and used in an appropriate ratio, an electrolyte having a higher electrical conductivity can be produced.

In addition, as the ether of the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether and ethylpropyl ether, or a mixture of two or more of them may be used. , But is not limited thereto.

And among the organic solvents, esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ -Any one or a mixture of two or more selected from the group consisting of valerolactone and ε-caprolactone may be used, but is not limited thereto.

The injection of the non-aqueous electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process of the final product and the required physical properties. That is, it can be applied before the electrochemical device assembly or at the final stage of assembly of the electrochemical device.

In this case, the electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples include capacitors such as all types of secondary cells, fuel cells, solar cells, or super capacitor devices. In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery is preferable among the secondary batteries.

Hereinafter, examples will be described in detail to specifically describe the present invention. 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 fully describe the present invention to those skilled in the art.

Example 1-1

LiNi ₈₅ Co ₁₀ Al ₅ O ₂ : Carbon black (Carbon black): The amount of the binder was weighed to be 96.5: 1: 2.5 by weight, and then mixed to prepare an electrode mixture slurry (viscosity: 15,000 cps). . As the binder, a mixture of 20 parts by weight of PVDF-HFP (molecular weight: about 600,000) was used based on 100 parts by weight of PVDF (molecular weight: about 1 million) and PVDF.

The electrode mixture slurry was applied to a thickness of 90 μm on an aluminum foil of 20 μm thickness. The electrode was prepared by rolling to a porosity of 30% and drying at 60° C. for 24 hours.

Example 1-2

The same electrode as in Example 1-1 was prepared except that PVDF-HFP (molecular weight: about 600,000) was added in 50 parts by weight.

Example 1-3

The same electrode as in Example 1-1 was prepared except that PVDF-HFP (molecular weight: about 600,000) was added in 80 parts by weight.

Comparative example 1-1

The same electrode as in Example 1-1 was prepared except that PVDF-HFP (molecular weight: about 600,000) was added in 10 parts by weight.

Comparative example 1-2

The same electrode as in Example 1-1 was prepared except that PVDF-HFP (molecular weight: about 600,000) was added in 90 parts by weight.

Example 2-1

LiNi ₈₅ Co ₁₀ Al ₅ O ₂ : Carbon black (Carbon black): The amount of the binder was weighed to be 96.5: 1: 2.5 by weight, and then mixed to prepare an electrode mixture slurry (viscosity: 15,000 cps). . For the binder, a mixture of 20 parts by weight of PVDF-CTFE (molecular weight: about 600,000) was used based on 100 parts by weight of PVDF (molecular weight: about 1 million) and PVDF.

The electrode mixture slurry was applied to a thickness of 90 μm on an aluminum foil of 20 μm thickness. The electrode was prepared by rolling to a porosity of 30% and drying at 60° C. for 24 hours.

Example 2-2

The same electrode as in Example 2-1 was prepared except that PVDF-CTFE (molecular weight: about 600,000) was added in 40 parts by weight.

Example 2-3

The same electrode as in Example 2-1 was prepared except that PVDF-CTFE (molecular weight: about 600,000) was added in 80 parts by weight.

Comparative example 2-1

The same electrode as in Example 2-1 was prepared except that PVDF-CTFE (molecular weight: about 600,000) was added in 10 parts by weight.

Comparative example 2-2

The same electrode as in Example 2-1 was prepared except that PVDF-CTFE (molecular weight: about 600,000) was added in 90 parts by weight.

Example 3-1

LiNi ₈₅ Co ₁₀ Al ₅ O ₂ : Carbon black (Carbon black): The amount of the binder was weighed to be 96.5: 1: 2.5 by weight, and then mixed to prepare an electrode mixture slurry (viscosity: 15,000 cps). . The binder contains PVDF (molecular weight: about 1 million), and a mixture of PVDF-HFP (molecular weight: about 600,000) and PVDF-CTFE (molecular weight: about 600,000) 1:1, based on 100 parts by weight of PVDF It was used by adding 30 parts by weight.

The electrode mixture slurry was applied to a thickness of 90 μm on an aluminum foil of 20 μm thickness. The electrode was prepared by rolling to a porosity of 30% and drying at 60° C. for 24 hours.

Example 3-2

The same electrode as in Example 3-1 was prepared except that a mixture of PVDF-HFP (molecular weight: about 600,000) and PVDF-CTFE (molecular weight: about 600,000) was added in 50 parts by weight.

Example 3-3

The same electrode as in Example 3-1 was prepared except that a mixture of PVDF-HFP (molecular weight: about 600,000) and PVDF-CTFE (molecular weight: about 600,000) was added in 70 parts by weight.

Comparative example 3-1

The same electrode as in Example 3-1 was prepared except that a mixture of PVDF-HFP (molecular weight: about 600,000) and PVDF-CTFE (molecular weight: about 600,000) was added in 20 parts by weight.

Comparative example 3-2

The same electrode as in Example 3-1 was prepared except that 80 parts by weight of a mixture of PVDF-HFP (molecular weight: about 600,000) and PVDF-CTFE (molecular weight: about 600,000) was added.

Electrode adhesion and C-rate test

The adhesive strengths of the electrodes of Examples 1-1 to 3-3 and Comparative Examples 1-1 to 3-2 and C-rate according to charging and discharging conditions were measured, and the results are shown in Table 1 below.

Adhesion (gf/cm) C-rate
0.5C/0.2C C-rate
1.0C/0.2C C-rate
2.0C/0.2C Example 1-1 136 94.9 89.1 69.1 Example 1-2 126 92.5 82.1 61.1 Example 1-3 112 90.6 77.1 48.5 Example 2-1 180 94.2 89.0 69.8 Example 2-2 175 94.5 89.0 71.0 Example 2-3 138 95.3 90.8 77.2 Example 3-1 115 94.8 89.0 69.7 Example 3-2 128 94.2 89.9 72.5 Example 3-3 132 94.6 88.6 70.0 Comparative Example 1-1 90 94.6 89.0 63.8 Comparative Example 1-2 75 81.5 68.5 33.1 Comparative Example 2-1 135 94.2 88.8 66.8 Comparative Example 2-2 85 95.6 90.6 77.2 Comparative Example 3-1 115 94.6 88.9 69.3 Comparative Example 3-2 116 92.8 85.2 65.2

It can be seen that the electrodes of Examples 1-1 to 3-3 according to the present invention include a second polymer binder in the above range, and thus have excellent charge and discharge rates and excellent adhesion to the electrodes.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical spirits within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (11)

Electrode current collector;
It is formed on one or both sides of the electrode current collector, the electrode active material layer comprising an electrode active material, a first polymer binder of polyvinylidene fluoride and a conductive material, includes,
The electrode active material layer further comprises 20 to 40 parts by weight of a second polymer binder, which is a copolymer of chlorotrifluoroethylene and polyvinylidene fluoride, based on 100 parts by weight of the first polymer binder,
The electrode having a weight average molecular weight of the first polymer binder is 1,000,000 to 1,300,000, and a weight average molecular weight of the second polymer binder being 400,000 to 600,000. According to claim 1,
The electrode is characterized in that the adhesive strength of the electrode is 100 gf / cm or more. delete delete According to claim 1,
An electrode characterized in that the content of chlorotrifluoroethylene in the copolymer of chlorotrifluoroethylene and polyvinylidene fluoride is 5 to 70% by weight. According to claim 1,
An electrode characterized in that the melting point of the first polymer binder is 100 to 200°C, and the melting point of the second polymer binder is 100 to 220°C. According to claim 1,
The electrode is an electrode, characterized in that the anode or cathode. According to claim 1,
The electrode active material layer is an electrode, characterized in that consisting of the product of the drying step of the slurry for the electrode. The method of claim 8,
The drying step, the electrode characterized in that it comprises a first drying step performed at a temperature of 120 to 140 ℃, and a second drying step performed in a vacuum of 80 to 100 ℃. In the electrochemical device comprising an anode, a cathode, a separator interposed between the anode and the cathode, and a non-aqueous electrolyte,
The positive electrode and the negative electrode are electrochemical devices of any one of claims 1, 2, and 5 to 9. The method of claim 10,
The electrochemical device is an electrochemical device, characterized in that a lithium secondary battery.