KR101488482B1 - Positive electrode active material and method of manufacturing the same, positive electrode and method of manufacturing the same, and electrochemical device having the positive electrode - Google Patents

Abstract

And a positive electrode active material layer formed on the current collector, wherein the positive electrode active material layer is composed of a positive electrode active material, and the positive electrode active material includes a material capable of doping and dedoping lithium, Wherein the conductive polymer coating layer is selected from a group consisting of a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer, and derivatives thereof A method for producing a positive electrode, a positive electrode active material, a method for producing a positive electrode active material, and an electrochemical device including the positive electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode, a method for producing the same, and an electrochemical device including the positive electrode }

A cathode, a method for producing the same, and an electrochemical device including the anode.

As small electronic devices such as high-performance notebook PCs, camcorders, PMPs, and smart phones are widely used, the demand for high capacity batteries is greatly increasing. In particular, due to the increase in high-end smart phones as well as notebook PCs, there is an increasing demand for high capacity lithium secondary batteries that can be used for a long time after one charge.

Also, with the development of high-capacity storage applications for use in hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), and electric vehicles (EV), the demand for high energy density cells is also increasing. In addition, miniaturization, thinning, and high capacity of lithium secondary batteries are continuously required.

The characteristics of such a battery largely depend on a material such as a cathode and a cathode which constitute the battery, and individual materials such as an anode, a cathode, a separator, and an electrolytic solution are actively developed. Particularly, since the capacity of a battery is mainly attributed to the active material properties of the positive electrode and the negative electrode, a large amount of active material has been studied.

In addition, there is a growing demand for a technique for effectively improving the productivity of a battery, such as a technique for effectively producing an electrode slurry, a technique for increasing an electrode production speed, and a technique for accelerating the penetration of an electrolyte into an electrode.

On the other hand, typical positive electrodes and negative electrodes include a binder and a conductive material.

The binder plays an important role in mechanically stabilizing the electrode. During the charging / discharging process of the battery, the active material or the conductive material is loosened due to the volume expansion of the active material, thereby increasing the contact resistance and degrading the characteristics of the battery. In order to solve such a problem, a polymer binder such as polyvinylidene fluoride or polytetrafluoroethylene is generally used. However, such a binder causes deterioration of life of the battery and lowers the initial efficiency.

The conductive material is added to improve the electron conductivity of the electrode, and usually carbon powder is used. When such a carbon powder is used, it is important to realize a state in which the carbon powder, the active material, and the binder are uniformly mixed during the production of the electrode slurry. However, carbon-based carbon black added in the conventional electrode manufacturing process is non-polar and hydrophobic, so that when using a water-soluble solvent, it is weak in wettability and tends to aggregate without being dispersed well. Therefore, in a conventional system using carbon black, an organic solvent having a high dielectric constant is used as a solvent. N-methyl pyrrolidone NMP (N-methyl pyrrolidone NMP) is used as a typical solvent. These organic solvents can adversely affect the environment. In particular, NMP is a bromine compound and is specified not to be released into the atmosphere.

Thus, the binder and the conductive material deteriorate the productivity of the battery and deteriorate the characteristics of the battery. However, in the conventional technology, it is inevitable to add a binder and a conductive material in order to improve the binding force and the electron conductivity of the electrode when preparing the electrode slurry.

One embodiment of the present invention is to provide a positive electrode having excellent binding power and electron conductivity even if it does not contain a binder and a conductive material but contains an active material, and a method for producing the same.

Another embodiment of the present invention is to provide an active material capable of realizing such a positive electrode and a manufacturing method thereof.

Another embodiment of the present invention is to provide an electrochemical device including the anode and having a simple manufacturing process, high production efficiency, high energy density, environment friendly, high rate characteristics, and excellent lifetime characteristics.

According to an embodiment of the present invention, there is provided a positive electrode comprising a current collector and a positive electrode active material layer formed on the current collector, wherein the positive electrode active material layer comprises only a positive electrode active material. The cathode active material includes a material capable of doping and dedoping lithium, and a conductive polymer coating layer formed on a surface of the material capable of doping and dedoping lithium. The conductive polymer coating layer includes at least one conductive polymer selected from polyacetylene-based polymers, polyaniline-based polymers, polypyrrole-based polymers, polythiophene-based polymers, polyphenylene-based polymers, and derivatives thereof.

The cathode active material layer may not include a binder and a conductive material.

The cathode active material itself can serve as a binder and a conductive material.

The conductive polymer may be, for example, polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) PEDOT), polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfone knit Polysulfur nitride (PSN), or a combination thereof.

The conductive polymer may be doped with an anion dopant.

The anion dopant may include a halogen anion, a halogenated anion, a sulfuric acid anion, a tosylate anion, a polyanion, or a combination thereof.

Specifically, the anion dopant may be chlorine ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate, or a combination thereof.

The weight ratio of the dopant to the conductive polymer may be 0.5 to 5.

The thickness of the conductive polymer coating layer may be 0.0001 to 5 mu m.

The material capable of doping and dedoping lithium may be at least one selected from the group consisting of lithium nickel based oxide, lithium cobalt based oxide, lithium nickel manganese based oxide, lithium nickel cobalt manganese based oxide, lithium nickel cobalt aluminum based oxide, lithium iron phosphate based oxide, Combinations thereof.

In another embodiment of the present invention, there is provided an electrochemical device including the above-described cathode, cathode, and electrolyte.

The electrochemical device may be a lithium secondary battery.

Another embodiment of the present invention provides a positive electrode active material comprising a material capable of doping and dedoping lithium, and a conductive polymer coating layer formed on a surface of the material capable of doping and dedoping lithium. The conductive polymer coating layer includes a conductive polymer doped with an anion dopant. The conductive polymer is a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer, or a derivative thereof. The anion dopant includes a halogen anion, a halogenated anion, a sulfuric acid anion, a tosylate anion, a polyanion, or a combination thereof.

The conductive polymer may be at least one selected from the group consisting of polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) , Polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfururon nitride, PSN), or a combination thereof.

The anion dopant may be chloride ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate, or a combination thereof.

The weight ratio of the anion dopant to the conductive polymer may be 0.5 to 5.

The thickness of the conductive polymer coating layer may be 0.0001 to 5 mu m.

According to another embodiment of the present invention, there is provided a method of preparing a conductive polymer solution, which comprises preparing a conductive polymer solution by mixing a conductive polymer and a first solvent, introducing a substance capable of doping and dedoping lithium into the conductive polymer solution, And removing the first solvent from the mixed solution to prepare a positive electrode active material having a conductive polymer coating layer formed on a surface of a material capable of doping and dedoping lithium. The conductive polymer includes a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer, or a derivative thereof.

The conductive polymer may be, for example, polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) PEDOT), polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfone knit Polysulfur nitride (PSN), or a combination thereof.

The conductive polymer may be doped with an anion dopant.

The anion dopant may include a halogen anion, a halogenated anion, a sulfuric acid anion, a tosylate anion, a polyanion, or a combination thereof. Specifically, the anion dopant may be chlorine ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate, or a combination thereof.

The weight ratio of the anion dopant to the conductive polymer may be 0.5 to 5.

The first solvent may be water, alcohol, acetone, tetrahydrofuran, cyclohexane, carbon tetrachloride, chloroform, methylene chloride, methanesulfonic acid, toluene, or combinations thereof.

According to another embodiment of the present invention, there is provided a method of manufacturing a positive electrode slurry, comprising: preparing a positive electrode slurry by mixing only a positive electrode active material prepared according to the above-described method with a second solvent; Of the present invention.

The second solvent may be, for example, water, acetone, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, N-methyl formamide, N-methyl pyrrolidone, or a combination thereof.

The method for producing the positive electrode may be such that the binder and the conductive material are not added to the positive electrode slurry.

According to another embodiment of the present invention, there is provided an electrochemical device comprising a cathode, a cathode, and an electrolyte prepared according to the above-described production method.

The electrochemical device may be a lithium secondary battery.

Other details of the embodiments of the present invention are included in the following detailed description.

The positive electrode according to one embodiment does not contain a binder and a conductive material but has excellent binding power and electron conductivity even when only an active material is included.

The electrochemical device according to another embodiment has a simple manufacturing process, high production efficiency, high energy density, environmental friendliness, high-rate characteristics, and excellent lifetime characteristics.

1 is a schematic view showing a lithium secondary battery according to one embodiment.
2 is a scanning electron microscope (SEM) image of the cathode active material prepared in Example 1. FIG.
3 is a scanning electron micrograph of the cathode active material prepared in Comparative Example 1. FIG.
FIG. 4 is a TEM electron micrograph of the cathode active material prepared in Example 1. FIG.
5 is a Raman analysis graph of the cathode active material prepared in Example 1 and Comparative Example 1. FIG.
Fig. 6 is a photograph of the positive electrode plate prepared in Example 1 wound around a glass rod having a radius of 0.5 cm, and Fig. 7 is a photograph taken around a glass rod having a radius of 0.25 cm.
8 is a photograph of a section of the positive electrode plate manufactured in Example 1. Fig.
9 is a photograph showing the distribution of sulfur by X-ray spectroscopic analysis of the cross section of the anode plate prepared in Example 1. Fig.
10 is a photograph of a section of a positive electrode after 100 cycles of the lithium secondary battery manufactured in Example 1. FIG.
FIGS. 11 and 12 are X-ray spectroscopic analysis of the anode section after 100 cycles of the lithium secondary battery produced in Example 1. FIG. 11 shows the distribution of sulfur, and FIG. 12 shows the distribution of carbon.
13 is a graph showing the discharge capacities of the lithium secondary batteries produced in Example 1 and Comparative Example 1 at a rate.
14 is a graph showing the charging / discharging lifetime characteristics of the lithium secondary battery manufactured in Example 1 and Comparative Example 1. Fig.
FIG. 15 is a graph showing the battery capacity converted into the capacity per unit volume of the positive electrode plate in FIG.
FIG. 16 is an AC impedance graph for the lithium secondary battery manufactured in Example 1 and Comparative Example 1, and FIG. 17 is an AC impedance graph measured after 100 cycles.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

According to an embodiment of the present invention, there is provided a positive electrode comprising a current collector and a positive electrode active material layer formed on the current collector, wherein the positive electrode active material layer is composed of only a positive electrode active material. The cathode active material includes a material capable of doping and dedoping lithium, and a conductive polymer coating layer formed on a surface of the material capable of doping and dedoping lithium.

The fact that the layer of the polarizing material is composed of only the cathode active material in the above means that the cathode active material layer does not contain the conductive material and the binder.

The conductive polymer coating layer forms an electron mobility network on the surface of a material capable of doping and dedoping lithium, and can serve as a conductive material. In addition, the conductive polymer coating layer has an adhesive force and can act as a binder.

Since such a cathode active material can serve as a binder and a conductive material by itself, even if the cathode active material layer does not contain a separate binder and a conductive material, the anode including the anode active material layer can realize excellent adhesion and electronic conductivity.

Also, since the cathode active material layer does not include a binder and a conductive material but contains only a cathode active material, energy density per electrode weight or electrode volume can be effectively improved.

The electrochemical device including the positive electrode is capable of charging / discharging at a high rate and has excellent lifetime characteristics.

In addition, since only the cathode active material and the solvent are used without using the binder and the conductive material in the preparation of the electrode slurry, the production process of the slurry becomes very simple and the production efficiency is increased. In addition, since the cathode active material is easily dispersed in a water-soluble solvent, it is environmentally friendly and economical.

The conductive polymer coating layer includes a conductive polymer, and the conductive polymer is at least one selected from the group consisting of a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene- .

The conductive polymer may be, for example, polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) PEDOT), polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfone knit Polysulfur nitride (PSN), and the like. Specifically, polyethylene dioxythiophene can be used.

Such a conductive polymer can form an electron mobility network at the surface of a substance capable of doping and dedoping lithium, and can have adhesiveness.

The conductive polymer may be doped with an anion dopant. The anion dopant can improve the electron conductivity of the conductive polymer coating layer.

The anion dopant may specifically include a halogen anion, a halogenated anion, a sulfuric acid anion, a tosylate anion, a polyanion, or a combination thereof. Specifically, the dopant may be chlorine ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate (PSS)

The weight ratio of the dopant to the conductive polymer may be 0.5 to 5. Specifically, the weight ratio may be 1 to 5, 0.5 to 4.5, 0.5 to 4, 0.5 to 3.5, and 0.5 to 3. In this case, the conductive polymer coating layer can realize excellent electron conductivity, thereby realizing a high capacity of the battery and improving the high-rate characteristics and the life characteristics.

The thickness of the conductive polymer coating layer may be 0.0001 to 5 mu m. Specifically, it may be 0.0001 to 1 占 퐉, 0.0001 to 0.5 占 퐉, 0.0001 to 0.1 占 퐉, and 0.001 to 0.1 占 퐉. When the thickness of the conductive polymer coating layer is in the above range, the conductive polymer coating layer can exhibit excellent adhesion and the problem of deterioration of battery performance due to increased resistance can be prevented.

The material capable of doping and dedoping lithium is not particularly limited as long as it is a material capable of oxidation-reduction reaction of lithium ions, and examples thereof include a lithium nickel oxide, a lithium cobalt oxide, a lithium nickel manganese oxide, lithium nickel cobalt manganese Based oxide, a lithium-nickel-cobalt-aluminum-based oxide, a lithium iron phosphate-based oxide, or a combination thereof.

That is, at least one of cobalt, manganese, nickel, or a composite oxide of a metal and lithium in combination thereof may be used. As a specific example thereof, a compound represented by any one of the following formulas can be used. Li _a A _{1 - b} R _b D ₂ wherein, in the formula, 0.90? A? 1.8 and 0? B? 0.5; Li _a E _{1 - b} R _b O _{2 - c} D _c , wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05; LiE _{2 - b} R _b O _{4 - c} D _{c where} 0? B? 0.5, 0? C? 0.05; Li _a Ni _{1 -b- c} Co _b R _c D _{α where} 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05, and 0 <α ≦ 2; Li _a Ni _{1 -bc} Co _b R _c O _2-α Z _α wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 <α <2; Li _a Ni _{1 -b- c} Co _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c D _? Wherein, in the formula, 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05, and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z _{? Where the} 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _{1 -b- c} Mn _b R _c O _{2 - ?} Z ₂ wherein 0.90? A? 1.8, 0? B? 0.5, 0? C? 0.05 and 0 <? Li _a Ni _b E _c G _d O ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1; Li _a Ni _b Co _c Mn _d GeO ₂ wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1; Li _a NiG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); Li _a MnG _b O ₂ wherein, in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1; Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90? A? 1.8 and 0.001? B? 0.1); QO _2; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiTO ₂ ; LiNiVO _4; Li _(3-f) J ₂ (PO ₄ ) ₃ (0? F? 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0? F? 2); And LiFePO _4.

In the above formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

Of course, a compound having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the compound. The coating layer may comprise, as a coating element compound, an oxide, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting these coating layers may be amorphous or crystalline. The coating layer may contain Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a mixture thereof. The coating layer forming step may be carried out by any of coating methods such as spray coating, dipping, and the like without adversely affecting the physical properties of the cathode active material by using these elements in the above compound. It is a content that can be well understood by people engaged in the field, so detailed explanation will be omitted.

As the current collector, aluminum, nickel, or the like may be used, but the present invention is not limited thereto.

Another embodiment of the present invention provides a method for producing a cathode active material. The method for producing a cathode active material includes the steps of preparing a conductive polymer solution by mixing a conductive polymer and a first solvent, adding a substance capable of doping and dedoping lithium to the conductive polymer solution to prepare a mixed solution, And removing the first solvent from the mixed solution to prepare a cathode active material having a conductive polymer coating layer formed on a surface of a material capable of doping and dedoping lithium.

The cathode active material produced according to this manufacturing method can serve as a binder and a conductive material. Therefore, the anode including the cathode active material can realize an excellent adhesive force and electronic conductivity without including the binder and the conductive material. In addition, the anode has a high energy density, and the electrochemical device including the anode has excellent high rate charge / discharge characteristics and life characteristics.

The description of the conductive polymer is as described above.

In the method of manufacturing the cathode active material, a dopant may be further added to the conductive polymer solution in the step of preparing the conductive polymer solution. That is, the conductive polymer may be doped with a dopant. The dopant can improve the electron conductivity of the conductive polymer coating layer. The dopant is described above.

The first solvent is a solvent for dispersing a substance capable of doping and dedoping lithium with the conductive polymer. The first solvent may be, for example, water, alcohol, acetone, tetrahydrofuran, cyclohexane, carbon tetrachloride, chloroform, methylene chloride, methanesulfonic acid, toluene, or combinations thereof.

Meanwhile, in the step of preparing the conductive polymer solution, an additive for improving the conductivity of the conductive polymer may be further added to the conductive polymer solution. The additive may be an alcohol, an organic solvent, an ionic liquid, an anionic surfactant, an acidic solution, or a combination thereof. The additive may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the conductive polymer.

According to another embodiment of the present invention, there is provided a method of manufacturing a positive electrode slurry, comprising: preparing a positive electrode slurry by mixing only a positive electrode active material prepared according to the above-described method with a second solvent; Of the present invention.

The second solvent may be, for example, water, acetone, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, N-methyl formamide, N-methyl pyrrolidone, or a combination thereof. In particular, since the cathode active material is well dispersed in an aqueous solvent, an aqueous solvent can be used as the second solvent. Therefore, the manufacturing method is environmentally friendly and economical.

In addition, since the positive electrode active material and the solvent are used alone without using a separate binder and a conductive material in manufacturing the positive electrode slurry, the manufacturing process is simple, economical, and high in production efficiency. Further, a positive electrode having a high energy density can be produced.

According to another embodiment of the present invention, there is provided an electrochemical device including the above-described cathode, cathode, and electrolyte. Or an electrochemical device comprising a cathode, a cathode, and an electrolyte prepared according to the above-described production method.

The electrochemical device may be a battery, a capacitor, or the like, and may be a lithium secondary battery.

A lithium secondary battery according to one embodiment will be described with reference to FIG. 1 is a schematic view showing a lithium secondary battery according to one embodiment. 1, a lithium secondary battery 100 according to an embodiment includes a cathode 114, a cathode 112 opposed to the anode 114, a separator 112 disposed between the anode 114 and the cathode 112, An electrode assembly including an electrode assembly 113 and an electrolyte (not shown) for impregnating the positive electrode 114, the negative electrode 112 and the separator 113; a battery container 120 containing the electrode assembly; And a sealing member 140 sealing the sealing member 120.

The anode 114 is as described above.

The negative electrode 112 includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As a material capable of reversibly intercalating / deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material. Typical examples thereof include crystalline carbon , Amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Q alloy (Q is an alkali metal, an alkaline earth metal, A transition metal, a rare earth element or a combination thereof and not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, an alkaline earth metal, A rare earth element or a combination thereof, but not Sn). The specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the anode active material particles to each other and to adhere the anode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

As the non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based or aprotic solvent may be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), and butylene carbonate (BC) may be used. As the ester solvent, methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate , Ethyl propionate,? -Butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone and the like can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. As the ketone solvent, cyclohexanone may be used have. As the alcoholic solvent, ethyl alcohol, isopropyl alcohol and the like can be used. As the aprotic solvent, R-CN (R is a C2 to C20 linear, branched or cyclic hydrocarbon group, An amide such as nitriles such as dimethylformamide, and dioxolanes such as 1,3-dioxolane, sulfolanes, and the like can be used.

The non-aqueous organic solvent may be used alone or in admixture of one or more. If the non-aqueous organic solvent is used in combination, the mixing ratio may be appropriately adjusted according to the desired cell performance. .

In the case of the carbonate-based solvent, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate. 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 non-aqueous organic solvent may further include the aromatic hydrocarbon-based organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of about 1: 1 to about 30: 1.

The aromatic hydrocarbon-based organic solvent may be an aromatic hydrocarbon-based compound represented by the following formula (A).

(A)

In Formula (A), R ₁₀₁ to R ₁₀₆ are each independently hydrogen, halogen, a C1 to C10 alkyl group, a C1 to C10 haloalkyl group, or a combination thereof.

The aromatic hydrocarbon-based organic solvent is selected from the group consisting of benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3- , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 - triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 - trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotol Ene, 1,2,3-tree-iodo toluene, 1,2,4-iodo toluene, xylene, or may be a combination thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound represented by the following formula (B) to improve battery life.

[Chemical Formula B]

Wherein R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group, and at least one of R ₇ and R ₈ Is a halogen group, a cyano group (CN), a nitro group (NO ₂ ) or a C1 to C5 fluoroalkyl group.

Representative examples of the ethylene carbonate-based compound include, for example, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, vinylene Ethylene carbonate, and the like. When the vinylene carbonate or the ethylene carbonate compound is further used, the amount of the vinylene carbonate or the ethylene carbonate compound can be appropriately controlled to improve the life.

The lithium salt is dissolved in the non-aqueous organic solvent to act as a source of lithium ions in the battery to enable operation of a basic lithium secondary battery, and a material capable of promoting the movement of lithium ions between the positive electrode and the negative electrode to be. The lithium salt Representative examples are _{LiPF 6, LiBF 4, LiSbF 6} , LiAsF 6, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2, LiAlCl 4, LiN (C x F 2x + 1 SO 2) (C y F 2y ₊₁ SO ₂₎ (where, x and y are natural numbers), LiCl, LiI, LiB ( C 2 O 4) 2 ( lithium bis oxalate reyito borate (lithium bis (oxalato) borate; LiBOB) , or in a combination thereof The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity Can exhibit excellent electrolyte performance, and lithium ions can effectively migrate.

The separator separates the negative electrode and the positive electrode and provides a passage for lithium ion, and any separator can be used as long as it is commonly used in a lithium battery. That is, it is possible to use an electrolyte having a low resistance to ion movement and an excellent ability to impregnate an electrolyte. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a polyolefin-based polymer separator such as polyethylene, polypropylene and the like is mainly used for a lithium ion battery, and a coated separator containing a ceramic component or a polymer substance may be used for heat resistance or mechanical strength, Structure.

Hereinafter, examples and comparative examples of the present invention will be described. The following embodiments are only examples of the present invention, and the present invention is not limited to the following embodiments.

( Example  One)

Preparation of cathode active material

A conductive polymer solution was prepared by dispersing PH1000, which is doped with polyethylene dioxythiophene (PEDOT), which is a conductive polymer, and polystyrene sulfonate (PSS), which is a dopant, in a weight ratio of 1: 2.5.

LiCoO ₂ particles were then added and kneaded for 30 minutes using an ultrasonic dispersing machine. After completion of the kneading, the LiCoO ₂ particles were recovered from the polymer solution and dried in an oven at 120 ° C. for 30 minutes to obtain a LiCoO ₂ particle surface-modified with a PEDOT polymer, that is, a cathode active material.

Manufacture of anode

A positive electrode slurry was prepared using the prepared positive electrode active material and water as a solvent. The prepared positive electrode slurry was applied to an aluminum foil current collector, dried at 120 ° C for 2 hours, and then rolled to produce a positive electrode.

Cathode manufacturing

Natural graphite as a negative active material, carbon black as a conductive material, and styrene-butadiene rubber (SBR) as a binder were mixed at a weight ratio of 93: 1: 6 to prepare an anode slurry. The prepared negative electrode slurry was applied to a copper foil current collector and dried at 110 DEG C for 2 hours to perform roll pressing to produce a negative electrode.

Manufacture of lithium secondary battery

As a separator, a separator made of polyethylene (Dornensa, F20BHE, thickness 20 μm) was used, and as the electrolyte, a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1: 1 was added to 1 M of lithium hexafluoro (LiPF ₆ ) was added to the solution.

A lithium secondary battery in the form of a coin cell was prepared using the prepared positive electrode and negative electrode, the separator, and the electrolyte solution.

( Comparative Example  One)

LiCoO ₂ as a cathode active material, carbon black as a conductive material, and PVdF as a binder were mixed at a weight ratio of 95: 2: 3, and a positive electrode slurry was prepared using an NMP solvent. The prepared positive electrode slurry was applied to an aluminum foil current collector, dried at 120 ° C for 2 hours, and then rolled to produce a positive electrode.

A lithium secondary battery was prepared using the prepared positive electrode and the subsequent procedure using the same method as in Example 1.

Evaluation example  1: Analysis of Conducting Polymer Coating Layer Using Scanning Electron Microscope

Field scanning electron microscope (FE-SEM) photographs of the cathode active materials prepared in Example 1 and Comparative Example 1 are shown in FIGS. 2 and 3, respectively.

Referring to FIGS. 2 and 3, the cathode active material prepared in Example 1 has a structure in which a conductive polymer coating layer is uniformly coated on the surface of LiCoO _{2 in} the form of a film, and an electron transfer network is formed between the active material and the active material Able to know.

Evaluation example  2: Analysis of Conducting Polymer Coating Layers Using Projection Electron Microscope

A TEM image of the cathode active material prepared in Example 1 is shown in FIG. Fig. 4 shows the morphology of the cathode active material of Example 1. Fig. Referring to the cathode active material morphology of FIG. 4, it can be seen that the conductive polymer coating layer is applied uniformly to a thickness of about 20 to 30 nm.

Evaluation example  3: Analysis of cathode active material by Raman analysis

The Raman analysis graph of the cathode active material prepared in Example 1 and Comparative Example 1 is shown in FIG. FIG. 5 shows that a conductive polymer coating layer was formed on the cathode active material of Example 1. FIG. Specifically, in Comparative Example 1, unlike Example 1, the graph of the graph of PEDOT inherent peak of 1508cm ^-1 of, 1432cm ^-1, 1367cm ^-1 peak is observed. It can be seen that the coating layer formed on the surface of the cathode active material through this peak exists in the PEDOT form.

Evaluation example  4: Anode exterior photograph

Fig. 6 is a photograph of the positive electrode plate prepared in Example 1 wound around a glass rod having a radius of 0.5 cm, and Fig. 7 is a photograph taken around a glass rod having a radius of 0.25 cm.

8 is a photograph of a section of the positive electrode plate manufactured in Example 1. Fig.

6 through 8, it can be seen that the positive electrode active material is well packed on the aluminum foil current collector. Even if the active material coated with the conductive polymer alone does not contain the binder and the conductive material, it can be confirmed that the positive electrode plate is well formed. From these results, it can be seen that the conductive polymer introduced on the surface of the positive electrode active material simultaneously acts as a conductive material and a binder.

Evaluation example  5: anode X-ray spectroscopic analysis of section ( Energy - dispersive  X- ray  spectroscopy, EDX )

FIG. 9 shows the result of analyzing a sulfur element as a component of the conductive polymer with respect to the cross section of the anode plate prepared in Example 1. FIG. Referring to FIG. 9, it can be seen that the sulfur component is evenly detected in the entire region in the electrode thickness direction. As a result, it can be seen that the conductive polymer is uniformly distributed over the entire area of the cathode active material.

Evaluation example  6: Analysis of anode cross section after cycling

FIG. 10 shows the distribution of sulfur (S) as a component of the conductive polymer by EDX analysis of the cross section of the anode, and FIG. And the distribution of carbon (C), another component of the conductive polymer, is shown in FIG.

Referring to FIG. 10, it can be seen that even after 100 cycles, the positive electrode active material is well coated on the aluminum foil current collector to maintain the shape of the electrode. Also, referring to FIGS. 11 and 12, it can be seen that the conductive polymer is evenly distributed in the electrode thickness direction even after 100 cycles.

Evaluation example  7: Lithium secondary battery By rate  Following Charging and discharging  Life characteristics

Experiments were conducted by varying the constant current rate of the lithium secondary battery manufactured in Example 1 and Comparative Example 1 using a charge / discharge device capable of constant current / constant potential control.

The constant current was applied at 0.2C (0.43 mAcm ^-2 ), 0.5C (1.06 mAcm ^-2 ), 1.0C (2.11 mAcm ^-2 ) and 2.0C (4.23 mAcm ^-2 ) Was set to 3.0 V (vs. Li / Li +) and the charge termination voltage was fixed to 4.2 V (vs. Li / Li +), respectively.

Fig. 13 shows the discharge capacities at the rate of Example 1 and Comparative Example 1. Fig. Referring to FIG. 13, it can be confirmed that the capacity of the first embodiment is substantially equivalent to that of the first comparative example.

Evaluation example  8: Lithium secondary battery Charging and discharging  Life characteristics

The charge and discharge cycles of the batteries manufactured in Example 1 and Comparative Example 1 were evaluated under a voltage of 3.0 V to 4.2 V using a charge and discharge device, and the results are shown in FIG. The experimental condition was a constant current of 1.0C (2.11 mAcm ^-2 ) / 1.0C.

Referring to FIG. 14, it can be seen that the capacity retention ratio of Example 1 is superior to that of Comparative Example 1 even after 100 cycles. As a result, it can be seen that the battery using the positive electrode plate made of only the positive electrode active material modified with the conductive polymer without the binder and the conductive material exhibits the same or better performance than the conventional battery.

Particularly noteworthy is the result of recalculating the battery capacity in terms of the capacity per unit volume of the anode plate. This is shown in Fig. Referring to FIG. 15, it can be seen that Example 1 exhibits a very large improvement in the capacity per volume of the positive electrode plate compared to Comparative Example 1 due to the absence of the binder and the conductive material.

Evaluation example  9: Impedance analysis

AC impedance was measured by varying the frequency from 0.01 to 10 ⁶ HZ using the VSP classic (Bio-Logic) equipment for the lithium secondary battery manufactured in Example 1 and Comparative Example 1. FIG. 16 is an AC impedance graph immediately after the lithium secondary battery was manufactured, and FIG. 17 is an AC impedance graph measured after 100 cycles.

Referring to FIG. 16, it can be seen that the first comparative example shows a value of about 30 ohm, whereas the first embodiment shows a value of 20 ohm or less. Referring to FIG. 17, it can be seen that the impedance of Comparative Example 1 is greater than 200 ohm after 100 cycles, whereas the impedance of Example 1 does not increase significantly after 100 cycles. As a result, it can be seen that the electric conductivity of the positive electrode prepared in Example 1 is more excellent and the phenomenon that the resistance of the battery increases can be suppressed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (27)

And a positive electrode active material layer formed on the current collector,
The positive electrode active material layer is composed of only a positive electrode active material,
Wherein the cathode active material comprises a material capable of doping and dedoping lithium and a conductive polymer coating layer formed on a surface of the material capable of doping and dedoping lithium,
Wherein the conductive polymer coating layer comprises at least one conductive polymer selected from a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer,
Wherein the cathode active material serves as a binder and a conductive material.
anode. delete The method of claim 1,
The conductive polymer may be selected from the group consisting of polyacetylene (PA), polyaniline (PANI), polypyrrole (PPy), polythiophen (PT), poly (3,4-ethylenedioxythiophene) ), Polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfuronitride polysulfur nitride (PSN), or a combination thereof. The method of claim 1,
Wherein the conductive polymer is doped with an anion dopant. 5. The method of claim 4,
Wherein the anion dopant comprises a halogen anion, a halogenated anion, a sulfate anion, a tosylate anion, a polyanion, or a combination thereof. 5. The method of claim 4,
The anion dopant is an anode which is a chloride ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate, or a combination thereof. 5. The method of claim 4,
Wherein the weight ratio of the anion dopant to the conductive polymer is 0.5-5. The method of claim 1,
Wherein the thickness of the conductive polymer coating layer is 0.0001 to 5 占 퐉. The method of claim 1,
The material capable of doping and dedoping lithium may be at least one selected from the group consisting of lithium nickel based oxide, lithium cobalt based oxide, lithium nickel manganese based oxide, lithium nickel cobalt manganese based oxide, lithium nickel cobalt aluminum based oxide, lithium iron phosphate based oxide, Anodes containing combinations. The positive electrode according to any one of claims 1 to 9,
Cathode, and
An electrochemical device comprising an electrolytic solution. 11. The method of claim 10,
Wherein the electrochemical device is a lithium secondary battery. A conductive polymer coating layer formed on a surface of a material capable of doping and dedoping lithium and a material capable of doping and dedoping lithium,
Wherein the conductive polymer coating layer comprises a conductive polymer doped with an anion dopant,
The conductive polymer may be a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer,
Wherein the anion dopant is selected from the group consisting of a halogen anion, a halogenated anion, a sulfate anion, a tosylate anion, a polyanion,
Which is a cathode active material and serves as a binder and a conductive material. The method of claim 12,
The conductive polymer may be at least one selected from the group consisting of polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) , Polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfururon nitride, PSN), or a combination thereof. The method of claim 12,
The anion dopant is a cathode active material which is a chloride ion (Cl ^- ), ClO ₄ ^- , sulfate ion (SO ₄ ^{2 -} ), polystyrene sulfonate, or a combination thereof. The method of claim 12,
Wherein the weight ratio of the anion dopant to the conductive polymer is 0.5-5. The method of claim 12,
Wherein the thickness of the conductive polymer coating layer is 0.0001 to 5 占 퐉. Preparing a conductive polymer solution by mixing the conductive polymer and the first solvent,
Adding a substance capable of doping and dedoping lithium to the conductive polymer solution to prepare a mixed solution, and
And removing the first solvent from the mixed solution to prepare a cathode active material having a conductive polymer coating layer formed on a surface of a material capable of doping and dedoping the lithium,
The conductive polymer includes a polyacetylene-based polymer, a polyaniline-based polymer, a polypyrrole-based polymer, a polythiophene-based polymer, a polyphenylene-based polymer, or a derivative thereof,
The prepared positive electrode active material serves as a binder and a conductive material.
A method for producing a cathode active material. The method of claim 17,
The conductive polymer may be at least one selected from the group consisting of polyacetylene (PA), polyaniline (PANI), polypyrrole PPy, polythiophen (PT), poly (3,4-ethylenedioxythiophene) , Polyisothianaphthene (PITN), polyphenylene vinylene (PPV), polyphenylene (PPE), polyphenylene sulfide (PPS), polysulfururon nitride, PSN), or a combination thereof. The method of claim 17,
Wherein the conductive polymer is doped with an anion dopant. 20. The method of claim 19,
Wherein the anion dopant comprises a halogen anion, a halogenated anion, a sulfuric acid anion, a tosylate anion, a polyanion, or a combination thereof. 20. The method of claim 19,
Wherein the weight ratio of the anion dopant to the conductive polymer is 0.5-5. The method of claim 17,
Wherein the first solvent is water, an alcohol, acetone, tetrahydrofuran, cyclohexane, carbon tetrachloride, chloroform, methylene chloride, methane sulfonic acid, toluene, or a combination thereof. Preparing a positive electrode slurry by mixing only the positive electrode active material prepared according to the production method of any one of claims 17 to 22 with a second solvent, and
Applying the positive electrode slurry to a collector and drying the positive electrode slurry
A method of manufacturing an anode. 24. The method of claim 23,
Wherein the second solvent is water, acetone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylformamide, methylpyrrolidone, or a combination thereof. 24. The method of claim 23,
Wherein the positive electrode slurry is not added with a binder and a conductive material. A positive electrode prepared according to the manufacturing method of claim 23,
Cathode, and
An electrochemical device comprising an electrolytic solution. 26. The method of claim 26,
Wherein the electrochemical device is a lithium secondary battery.

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