KR20130117930A - The anode electrodes and the secondary battery comprising the same - Google Patents

Abstract

PURPOSE: A negative electrode for a secondary battery improves the ion conductivity by spreading a negative electrode mixture in a three dimensional stereographic pattern onto a current collector, thereby improving the output performance and rate performance of a secondary battery. CONSTITUTION: In a negative electrode for a secondary battery, a negative electrode mixture including a negative electrode active material, a binder, and a conducting material are spread onto a current collector. The negative electrode mixture has a three dimensional stereographic pattern and is spread onto the current collector, thereby improving ion conductivity. The gap between the three dimensional stereographic patterns is 0.1-100 nm. The thickness of the three dimensional stereographic pattern is 0.1-100 nm. The area of the three dimensional stereographic pattern is 50-90% of that of the current collector. The negative electrode uses a lithium titanium oxide as a negative active material.

Description

Anode and a secondary battery comprising the same {The Anode Electrodes and the Secondary Battery Comprising the Same}

The present invention relates to a negative electrode for a secondary battery having a negative electrode mixture including a negative electrode active material, a binder, and a conductive material applied to a current collector, and a secondary battery including the same, wherein the negative electrode mixture is formed on a current collector in a three-dimensional solid structure pattern. It relates to a secondary battery negative electrode and a secondary battery comprising the same, characterized in that applied to improve the ion conductivity.

As technology development and demand for mobile devices have increased, there has been a rapid increase in demand for secondary batteries as energy sources. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operational potential, long cycle life, Batteries have been commercialized and widely used.

In recent years, there has been a growing interest in environmental issues, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs), which can replace fossil-fueled vehicles such as gasoline vehicles and diesel vehicles, And the like. Although a nickel metal hydride (Ni-MH) secondary battery is mainly used as a power source for such an electric vehicle (EV) and a hybrid electric vehicle (HEV), a lithium secondary battery having a high energy density, a high discharge voltage, Research is being actively carried out, and some are commercialized.

Conventional lithium ion secondary batteries use a lithium cobalt composite oxide for the positive electrode and a graphite-based material for the negative electrode. However, in recent years, a spinel-structured lithium nickel-based metal oxide is used for the positive electrode. , Researches on using lithium titanium oxide or the like as a negative electrode active material have been much progressed.

In such a lithium secondary battery, charging and discharging proceed while repeating a process in which lithium ions of a positive electrode are inserted into and detached from a negative electrode. The theoretical capacity of the battery is different depending on the type of the electrode active material, but as the cycle progresses, the charge and discharge capacity is generally lowered.

This phenomenon is the biggest cause of the separation of the electrode active material or between the electrode active material and the current collector due to the change of the volume of the electrode caused by the progress of the charging and discharging of the battery, so that the active material fails to function. In addition, during the insertion and desorption process, lithium ions inserted into the negative electrode do not escape properly, thereby reducing the active point of the negative electrode. As a result, the charge and discharge capacity and life characteristics of the battery may decrease as the cycle progresses.

Therefore, there is a great need for a technology capable of improving battery performance by securing adhesion between the active material and the current collector and exhibiting excellent ion conductivity while improving battery performance.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

After extensive research and various experiments, the inventors of the present application have a desired effect when the negative electrode mixture is applied onto the current collector in a pattern of a predetermined three-dimensional solid structure on the current collector, as described later. It was confirmed that can be achieved, and came to complete the present invention.

Accordingly, the present invention is a negative electrode for a secondary battery in which a negative electrode mixture including a negative electrode active material, a binder, and a conductive material is applied to a current collector, wherein the negative electrode mixture is applied onto a current collector in a pattern of a three-dimensional solid structure to improve ion conductivity. Provided is a negative electrode for a secondary battery, which is improved.

In one preferred embodiment, the pattern may form points, lines or faces.

The shape of the three-dimensional solid structure may be polyhedral, cylindrical or conical.

The three-dimensional solid structure may be formed at intervals of 0.1 to 100 nm, may be formed to a thickness of 0.1 to 100 nm, it may be formed of an area of 50 to 90% based on the area of the current collector.

The present invention provides a secondary battery comprising the negative electrode.

The negative electrode may use lithium titanium oxide (LTO) as a negative electrode active material, and preferably Li _x Ti _y O ₄ (0.5 ≦ _x ≦ 3; 1 ≦ _y ≦ 2.5).

The secondary battery according to the present invention is preferably a lithium secondary battery.

Also, the present invention provides a battery module including the secondary battery as a unit battery, a battery pack including the battery module, and a device including the battery pack.

The device may be an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage.

As described above, in the negative electrode for secondary battery according to the present invention, since the negative electrode mixture including the negative electrode active material, the binder, and the conductive material is applied onto the current collector in a three-dimensional three-dimensional structure pattern, the ion conductivity is improved and excellent output Characteristics and rate characteristics.

The present invention is a negative electrode for a secondary battery in which a negative electrode mixture including a negative electrode active material, a binder, and a conductive material is applied to a current collector, wherein the negative electrode mixture is applied onto a current collector in a three-dimensional solid structure pattern to improve ion conductivity. It provides a negative electrode for a secondary battery, characterized in that.

When the negative electrode mixture is applied to the surface of the current collector in a three-dimensional solid structure pattern, the lithium ions between the current collector and the negative electrode active material are smoothly transferred, and the contact area with the electrolyte is increased, thereby improving the lithium ion conductivity. Not only can the internal resistance of the battery be reduced, but also the output and rate characteristics can be improved.

Patterns in the form of these three-dimensional solid structures may vary, for example, may form points, lines, or faces.

Although the shape of the three-dimensional solid structure is not limited, for example, a polyhedral, cylindrical or conical pattern may be formed uniformly.

That is, the negative electrode mixture may be applied to the current collector in the form of a three-dimensional solid structure such as a polyhedron, a cylindrical shape, or a conical shape as defined above. Can be formed.

In this case, the shape of the three-dimensional solid structure may preferably be formed at intervals of 0.1 to 100 nm, and the thickness of the three-dimensional solid structure may be preferably formed at 0.1 to 100 nm, more preferably. Preferably, the spacing and thickness of the three-dimensional solid structure may be formed in 10 to 80 nm, respectively. In addition, the three-dimensional solid structure may be formed with an area of 50 to 90%, preferably 60 to 85% based on the area of the current collector.

If the spacing and thickness of the three-dimensional solid structure is too thin or the area in which the three-dimensional solid structure is formed is small, it is difficult to expect an improvement in ion conductivity, and conversely, the spacing and thickness of the three-dimensional solid structure are too thick or If the formed area is large, the width of the internal resistance increase may increase, thereby degrading the performance of the battery.

There is no particular limitation as long as it is known in the art as a method of forming a three-dimensional solid structure on the surface of the current collector, preferably, it may be made by a method such as spray coating, pattern coating, deposition or etching. Such methods and the like are known in the art, and thus detailed descriptions thereof will be omitted below.

The present invention provides a secondary battery comprising the negative electrode.

The negative electrode is manufactured by coating, drying, and pressing a negative electrode active material on a negative electrode current collector, and optionally, the conductive material, binder, filler, and the like as described above may be further included.

The negative electrode current collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The negative electrode active material may include, for example, carbon such as non-graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Au _x Me _{1 - x} Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{AuO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide and the like can be used.

In one example, when lithium titanium oxide (LTO) is used as the negative electrode active material, the electrode structure as described above is preferable because the electron conductivity of LTO itself is low. In this case, the spinel lithium manganese composite oxide having LiNi _x Mn _2-x O ₄ (x = 0.01 to 0.6) having a relatively high potential due to the high potential of LTO is preferably used as the positive electrode active material.

The secondary battery according to the present invention also includes a positive electrode.

The positive electrode for a secondary battery is prepared by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, followed by drying and pressing. If necessary, a filler may be further added to the mixture.

The positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel and aluminum , Nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, or the like on the surface of aluminum or stainless steel may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; The formula Li _{1 + x} Mn _{2 - x} O ₄ (Where x is 0 to 0.33), lithium manganese oxides such as LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A Ni-site type lithium nickel oxide expressed by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); Formula _{LiMn 2-x M x O 2} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); Spinel-structure lithium manganese composite oxides such as LiNi _x Mn _2-x O ₄ (x = 0.01 to 0.6); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but is not limited to these, preferably LiNi _0.5 Mn _1.5 O ₄ or LiNi _0.4 Mn _1.6 O ₄ It may be.

The conductive material is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, for example, graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskeys 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.

The binder is a component that assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 50 wt% based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber are used

In addition, the secondary battery has a structure in which a lithium salt-containing electrolyte is impregnated in an electrode assembly having a separator interposed between the positive electrode and the negative electrode.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte solution containing the lithium salt is composed of an electrolyte solution and a lithium salt. The electrolyte solution may be a non-aqueous organic solvent, an organic solid electrolyte, or an inorganic solid electrolyte, but is not limited thereto.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.

For the purpose of improving the charge / discharge characteristics and the flame retardancy, the electrolytic solution is preferably mixed with an organic solvent such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, . In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further added to impart nonflammability. In order to improve the high-temperature storage characteristics, carbon dioxide gas may be further added. FEC (Fluoro-Ethylene Carbonate, PRS (Propene sultone), and the like.

In a preferred _{embodiment, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

The present invention also provides a battery module including the secondary battery as a unit cell, and a battery pack including the battery module.

The battery pack can be used as a power source for a medium and large-sized device requiring high temperature stability, long cycle characteristics, and high rate characteristics.

Preferred examples of the above medium to large devices include a power tool that is powered by an electric motor and moves; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (14)

A negative electrode for secondary battery in which a negative electrode mixture including a negative electrode active material, a binder, and a conductive material is applied to a current collector, wherein the negative electrode mixture is coated on a current collector in a pattern of a three-dimensional solid structure to improve ion conductivity. Secondary battery negative electrode. The negative electrode of claim 1, wherein the pattern forms a dot, a line, or a surface. The negative electrode for a secondary battery of claim 1, wherein the three-dimensional solid structure has a polyhedron, a cylindrical shape, or a conical shape. The negative electrode for a secondary battery according to claim 1, wherein an interval of the three-dimensional solid structure is 0.1 to 100 nm. The negative electrode for a secondary battery of claim 1, wherein the three-dimensional structure has a thickness of 0.1 to 100 nm. The negative electrode for a secondary battery of claim 1, wherein the three-dimensional solid structure is formed in an area of 50 to 90% based on the area of the current collector. A secondary battery comprising the negative electrode according to any one of claims 1 to 6. The secondary battery of claim 7, wherein the negative electrode uses lithium titanium oxide (LTO) as a negative electrode active material. The secondary battery of claim 8, wherein the lithium titanium oxide is represented by Li _x Ti _y O ₄ (0.5 ≦ _x ≦ 3; 1 ≦ _y ≦ 2.5). The secondary battery according to claim 7, wherein the secondary battery is a lithium secondary battery. A battery module comprising the secondary battery according to claim 10 as a unit cell. A battery pack comprising the battery module according to claim 11. Device comprising a battery pack according to claim 12. The device of claim 13, wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a system for power storage.