KR20120093487A - Anode having multi-layer structure for secondary battery and lithium secondary battery including the same - Google Patents

Abstract

PURPOSE: A negative electrode of a multi-layered structure for a secondary battery is provided to improve wettability, to have excellent safety and stability, while having high energy density and high output performance. CONSTITUTION: A negative electrode of a multi-layered structure for a secondary battery comprises a first negative electrode mixture layer comprising a first negative electrode active material spread in state contacted to a surface of a current collector, and a second negative electrode mixture layer comprising a second negative electrode material spread on the first negative electrode active material, having relatively higher charging/discharging voltage and relatively higher hydrophilicity than the first negative electrode active material. Hydrophobicity of the negative electrode active material to electrolyte is 20-300% higher than the first negative electrode active material.

Description

Anode Having Multi-Layer Structure for Secondary Battery and Lithium Secondary Battery Including The Same}

The present invention relates to a negative electrode for a secondary battery having a multilayer structure and a lithium secondary battery including the same, and more particularly, a first negative electrode mixture layer comprising a first negative electrode active material applied in contact with a surface of a current collector; A multi-layer structure comprising a second negative electrode mixture layer coated on the first negative electrode mixture layer and including a second negative electrode active material having a relatively higher charge / discharge potential and a relatively higher hydrophilicity than the first negative electrode active material. It relates to a secondary battery negative electrode and a lithium secondary battery comprising the same.

Increasing the price of energy sources due to the depletion of fossil fuels, interest in environmental pollution is increasing, and the demand for environmentally friendly alternative energy sources is becoming an indispensable factor for future life. Accordingly, researches on various power production technologies such as nuclear power, solar energy, wind power, tidal power, etc. continue, and power storage devices for more efficient use of the generated energy are also drawing attention.

In particular, in the case of lithium secondary batteries, as the development and demand for mobile devices increases, the demand for energy sources is rapidly increasing, and in recent years, the use of electric vehicles (EVs) and hybrid electric vehicles (HEVs) as power sources has been realized. In addition, the use area is also being expanded for grid auxiliary.

Lithium secondary batteries used as power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs) have high energy density and high power output in a short time, and under severe conditions where charging and discharging by a large current is repeated in a short time. Since it should be able to be used for more than 10 years, it is inevitably required to have superior safety and long life characteristics than conventional small lithium secondary batteries.

In addition, a lithium secondary battery used as a large-capacity power storage device has to have a high energy density and efficiency and a long lifespan, as well as safety and reliability because fire or explosion accidents are linked to large accidents when a system malfunctions due to high performance and high capacity. Ensuring that is especially important.

In this regard, a negative electrode of a conventional lithium secondary battery is a carbon-based compound capable of intercalation and detachment of reversible lithium ions while maintaining structural and electrical properties as a negative electrode active material.

Specifically, the carbon-based compound has a very low discharge potential of about -3V with respect to the standard hydrogen electrode potential, exhibits a very reversible charge and discharge behavior due to the uniaxial orientation of the graphite layer, thereby resulting in an excellent electrode It shows higher cycle life and also shows higher potential when constructing an oxide-based anode and cell because the electrode potential during charging of Li ions can exhibit a potential similar to that of pure lithium metal as 0 V Li / Li ⁺ . It has the advantage of obtaining energy.

However, the negative electrode made of such a carbon-based compound has the following problems.

First, the carbon-based compound has a theoretical maximum capacity of 372 mAh / g (844 mAh / cc), which is limited in capacity increase, making it difficult to play a sufficient role as an energy source of a rapidly changing next-generation mobile device.

Second, since the chemical potential of the carbon-based compound is similar to that of metallic lithium in the insertion and desorption of lithium ions, lithium precipitation occurs due to overpotential even at a slight high charging current, and once deposited lithium is charged As the discharge is repeated, there is a problem that the acceleration may be further accelerated and cause short-circuit through dendrite, which may greatly affect safety.

Third, when more lithium is charged than the amount of lithium that can be received from the negative electrode due to overcharging of the battery, the temperature rises and an exothermic reaction occurs. This is because of the earliest reaction among the thermodynamic reactions occurring inside the battery. One can be a major trigger, such as a battery ignition explosion.

Fourth, the surface of the hydrophobic electrode has a great influence on the electrode wetting of the electrolyte during battery production, and this electrode wetting time affects the productivity of the battery.

In order to solve the above problems, a recent study on the negative electrode material and Li ₄ Ti ₅ O ₁₂ by the Li alloy-based reaction using silicon (Si), tin (Sn) away from the conventional carbon-based negative electrode material There is a lot going on.

However, silicon, for example, has a theoretical maximum capacity of about 4020 mAh / g (9800 mAh / cc, specific gravity 2.23), which is a significant advantage over graphite based materials. It has the disadvantage that the volume change during charge and discharge is very large.

In addition, Li ₄ Ti ₅ O ₁₂ has a very low structural change during charging and recharging, which is a zero-strain material having excellent life characteristics, forming a relatively high voltage range, and generating dendrite crystals. It is known as a material having excellent safety and stability, and also has the advantage of having a quick charging electrode property that can be charged within a few minutes, but has a very low capacity and a voltage for use as a negative electrode. There is a problem that the energy density is very low and very high.

In addition, Patent Application Publication Nos. 2010-0008785, 2008-0112977, 2010-0086367, and 2006-0028327 disclose a negative electrode active material in which a titanium-containing oxide is placed or coated on a surface of a carbon-based negative electrode active material. However, manufacturing a negative electrode active material having a titanium-containing oxide on the surface is difficult to be mixed with each other due to the opposite characteristics of the two materials, and there is a problem that involves a cost increase in the process.

Therefore, there is an urgent need for development of a cathode having improved safety and stability, high output characteristics and high energy density that can be used as a high capacity power source.

On the other hand, high wetting properties are becoming more important as the area of medium and large devices is increased for high capacity, and since the formation of dendritic crystals occurs from the surface of the electrode, simple mixing of a carbon-based negative electrode active material and a titanium-containing oxide is performed. There is a problem that it is not easy to maximize the wettability.

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.

The inventors of the present application, after continuing in-depth research and various experiments, notice that the formation of dendrite, the electrode wetting of the electrolyte, and the electrochemical reaction with the electrolyte arise from the surface reaction of the electrode. When the second negative electrode mixture including the second negative electrode active material having a relatively high charge and discharge potential and a large hydrophilicity compared to the first active material in the first negative electrode mixture on the first negative electrode mixture applied to the current collector surface . The present inventors have found that they have high energy density while improving safety and stability, and have completed the present invention.

Accordingly, an object of the present invention is to provide a secondary battery negative electrode having a high energy density, high output characteristics and a lithium secondary battery including the same while improving safety and stability.

In order to solve the above problems, a negative electrode for a secondary battery according to the present invention includes a first negative electrode mixture layer comprising a first negative electrode active material applied in contact with a surface of a current collector; And a second negative electrode mixture layer coated on the first negative electrode mixture layer and including a second negative electrode active material having a relatively higher charge / discharge potential and a relatively higher hydrophilicity than the first negative electrode active material. Characterized in that the multilayer structure comprising a.

Accordingly, the negative electrode for secondary batteries according to the present invention is coated on the first negative electrode mixture by applying a second negative electrode mixture including a second negative electrode active material having a relatively high charge and discharge potential compared to the first negative electrode active material in the first negative electrode mixture In addition, the formation of dendrite is prevented to improve safety.

Specifically, the second negative electrode mixture formed on the surface of the negative electrode which reacts directly with the electrolyte solution is charged to the second negative electrode mixture when lithium is charged in the negative electrode, thereby acting as a kind of buffer for a large amount of current charge. Therefore, formation of dendritic crystals due to repetitive charge and discharge is prevented on the surface of the second negative electrode active material having a higher charge and discharge potential than the first negative electrode active material similar to the charge and discharge potential of lithium metal.

In addition, the negative electrode for secondary batteries according to the present invention by applying a second negative electrode mixture comprising a second negative electrode active material having a relatively larger hydrophilicity than the first negative electrode active material in the first negative electrode mixture on the first negative electrode mixture, Improves the wetting of

Specifically, the second negative electrode mixture formed on the surface of the negative electrode that reacts directly with the electrolyte serves to lower the surface tension so that the electrolyte can be easily impregnated on the surface of the negative electrode, and has a relatively hydrophobicity compared to the second negative electrode active material. In the negative electrode active material, the permeated electrolyte solution penetrates to the surface portion of the negative electrode current collector by a capillary phenomenon to improve the electrolyte wettability.

The affinity for the electrolyte of the second negative electrode active material may be 20 to 300% greater than that of the first negative electrode active material when expressed as an affinity for the polar material. As an example of evaluating affinity for an electrolyte solution that is a polar material, when the electrolyte solution impregnation rate is compared, the impregnation rate of the electrolyte solution for the second negative electrode mixture layer may be, for example, 30 to 200% greater than that of the first negative electrode active material.

If the affinity of the second negative electrode active material for the electrolyte, for example, the electrolyte impregnation rate is not greater than the range above the first negative electrode active material, it may be difficult to achieve the desired effects in the present invention as described above Not.

The first negative electrode active material may be at least one selected from the group consisting of crystalline graphite and low crystalline carbon. In one preferred example, the mixture may be a mixture of the flaky crystalline graphite carbon compound and the low crystalline carbon compound.

In general, crystalline carbon-based compounds have a two-dimensional path for lithium ions to be inserted and desorbed into the layered structure of carbon, whereas low-crystalline carbonated compounds have a limited path for insertion of lithium ions. Since it is relatively large, it exhibits excellent rate characteristics. However, the amorphous carbon-based compound has a very high disadvantage as the irreversible capacity is about 20 to 30%.

On the other hand, as described above, by including the flake-like crystalline carbon-based compound having a relatively low irreversible capacity in the amorphous carbon-based compound as the first negative electrode active material, to compensate for the above disadvantages.

In some cases, the first negative electrode active material may have a form in which low crystalline carbon is coated on a crystalline graphite core.

The first negative electrode active material is spherical, the crystalline graphite may be natural graphite or artificial graphite, the low crystalline carbon (carbon) is particularly limited as long as the carbon atoms have an amorphous crystal structure and exhibit excellent rate characteristics For example, hard carbon, coke, needle coke or pitch carbonized carbon obtained by pyrolyzing a phenol resin or a furan resin may be used.

Therefore, the secondary battery negative electrode according to the present invention may have a high energy density by using a carbon-based compound having a high energy density as the first negative electrode active material.

On the other hand, the second negative electrode active material may be preferably a titanium containing oxide. The titanium-containing oxide may be, for example, at least one selected from the group consisting of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) and titanium dioxide (TiO ₂ ), preferably lithium titanium oxide (Li ₄ Ti _5). O ₁₂ ).

In some cases, the second negative electrode active material may be a mixture of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) and titanium dioxide (TiO ₂ ), and in this case, their content ratio is 10:90 to 10 based on the weight ratio. It may be in the range of 90:10.

Therefore, the negative electrode for secondary batteries according to the present invention improves cycle characteristics because structural stability is maintained during repeated charging and discharging by using titanium-containing oxide as the second negative electrode active material.

The negative electrode includes a first negative electrode mixture layer and a second negative electrode mixture layer prepared by adding and stirring the negative electrode active material to a dispersion, preparing a paste, and then applying and drying the negative electrode current collector. The mixture layers may optionally further include components such as a conductive agent, a binder, and a filler.

In the process, the negative electrode mixture layer of the multilayer structure according to the present invention may be formed by a single double coating process, thereby reducing the process cost and the like by simplifying the process.

The negative electrode 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 conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, 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, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), cellulose, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose Roses, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like. .

The conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, graphite carbon black such as natural graphite or artificial graphite, acetylene black, Ketjen black, channel black, furnace, etc. Carbon black such as black, lamp black, summer black, conductive fiber such as carbon fiber or metal fiber Metal fluoride such as carbon fluoride, aluminum, nickel powder, etc. Conductive metal oxide polyphenylene, such as zinc oxide, conductive whiskey titanium oxide such as potassium titanate Conductive materials such as derivatives and the like can be used. Specific examples of commercially available conducting agents include acetylene black Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, EC series (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

In some cases, a filler may be optionally added as a component to suppress the expansion of the negative electrode. The filler is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. For example, fibrous materials such as olefinic polymer glass fibers such as polyethylene and polypropylene, and carbon fibers are used.

As the dispersion, isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like may be typically used.

The method of evenly applying the paste of the electrode material to the metal material can be selected from known methods or performed by a new suitable method in consideration of the properties of the material. For example, it is preferable to disperse the paste onto the current collector and then to disperse the paste uniformly using a doctor blade or the like. In some cases, a method of distributing and dispersing in one process may be used. In addition, die casting, comma coating, screen printing, or the like may be used. Alternatively, molding on a separate substrate may be performed by pressing or lamination. You may join.

Drying of the paste applied on the metal plate is preferably dried for 1 to 3 days in a vacuum oven at 50 to 200 ℃.

In addition, the present invention includes a positive electrode including at least one selected from the above-described negative electrode, the positive electrode active material for lithium secondary batteries represented by Formula 1 and Formula 2, and a porous separator interposed between the negative electrode and the positive electrode It provides an electrode assembly for a secondary battery consisting of.

Li _x (Ni _v Mn _w Co _y M _z ) O _2-t A _t (1)

Where

0.8 <x ≦ 1.3, 0 ≦ v ≦ 0.9, 0 ≦ w ≦ 0.9, 0 ≦ y ≦ 0.9, 0 ≦ z ≦ 0.9, x + v + w + y + z = 2, 0 ≦ t <0.2;

M is at least one metal or transition metal cation of +2 to + 4-valent oxidation number and A is -1 or -divalent anion.

Li _a Mn _2-b M ' _b 0 _4-c A' _c (2)

Where

0.8 <a ≦ 1.3, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.3;

M 'is at least one metal or transition metal cation of +2 to + 4-valent oxidation number and A' is -1 or -divalent anion.

In Formula 1, a transition metal such as Ni, Mn, Co, etc. may be substituted with a metal of + 2-valent to + 4-valent oxidation number and / or other transition metal (M) element, preferably Al, Mg, and Ti. It may be substituted with one or more selected from the group consisting of, in this case the preferred amount of substitution may be 0.3≤z≤0.6.

M ′ in Formula 2 may be at least one selected from the group consisting of Co, Mn, Ni, Al, Mg, and Ti.

In addition, the oxygen ions in the general formula (1) and (2) can be replaced with anions (A, A ') of the oxidation number -1 or -divalent in a predetermined range, A and A' are preferably independently of each other F It may be one or more selected from the group consisting of halogen, such as Cl, Br, I, S and N.

By substituting these anions, the binding force with the transition metal is improved and the structural transition of the compound is prevented, so that the lifetime of the battery can be improved. On the other hand, if the amount of substitution of the anions A and A 'is too large (t> 0.2), it is not preferable because the life characteristics are lowered due to the incomplete crystal structure.

In one preferred embodiment, the positive electrode active material represented by the formula (1) includes a mixed transition metal of Ni and Mn, the average oxidation number of all transition metals except lithium is greater than +3, the content of nickel on the basis of molar ratio of manganese It may be a lithium transition metal oxide of a layered structure satisfying a condition equal to or greater than the content.

In another preferred example, the cathode active material represented by Chemical Formula 1 may be Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ or Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ .

The manufacturing method of the positive electrode which concerns on this invention is not specifically limited, One example is demonstrated below.

A binder and a conductive agent were added to the dispersion in an amount of 1 to 20% by weight with respect to the composite positive electrode active material and stirred to prepare a paste, and then coated on a metal plate for current collector, compressed, and dried to prepare a laminate electrode. can do.

The positive electrode current collector is generally made to a thickness of 3 to 500㎛. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like can be used.

Like the negative electrode current collector, the current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The separator 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 ~ 10㎛, the thickness is generally 5 ~ 300㎛. As such a separator, for example, a sheet made of an olefin polymer glass fiber or polyethylene such as polypropylene having chemical resistance and hydrophobicity, a nonwoven kraft paper, or the like is used. Typical examples currently on the market include Celgard series (Celgard ^R 2400, 2300 (manufactured by Hoechest Celanese Corp.), polypropylene separator (manufactured by Ube Industries Ltd. or Pall RAI), polyethylene series (Tonen or Entek), etc.).

In some cases, a gel polymer electrolyte may be coated on the separator to increase battery stability. Representative examples of such gel polymers include polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and the like.

The present invention also provides a lithium secondary battery in which the electrode assembly is impregnated with an electrolyte. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The said lithium salt containing non-aqueous electrolyte consists of a nonaqueous electrolyte and lithium. As the non-aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, for example , Gamma-butylo lactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, 4-methyl-1,3-dioxene, diethyl ether, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxolon Aprotic organic solvents such as derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used. Can be.

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, Polymers containing ionic dissociation groups, and the like can be used.

As the inorganic solid electrolyte, for example, 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, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may 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 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenylborate, imide, and the like can be used.

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, in order to impart nonflammability, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate) may be further included. ), PRS (Propene sultone) may be further included.

Since the secondary battery according to the present invention exhibits high energy density, high output characteristics, improved safety and stability, it may be particularly preferably used as a constituent battery of a medium and large battery module. Accordingly, the present invention also provides a medium-large battery module including the secondary battery as a unit cell.

The medium-large battery module may be preferably applied to a power source that requires high output and large capacity, such as an electric vehicle, a hybrid electric vehicle, and a power storage device.

Since the construction of the medium-large battery module and its manufacturing method are well known in the art, a description thereof will be omitted.

The negative electrode for a secondary battery according to the present invention prevents the formation of dendritic crystals by applying a second negative electrode mixture including a second negative electrode active material having a higher charge and discharge potential on the first negative electrode mixture than the first negative electrode active material. It has the effect of improving safety.

In addition, the negative electrode for a secondary battery according to the present invention improves the wetting of the electrolyte by applying a second negative electrode mixture including a second negative electrode active material having a relatively larger hydrophilicity than the first negative electrode active material on the first negative electrode mixture. It is effective to let.

In addition, the negative electrode for a secondary battery according to the present invention has a high energy density by using a carbon-based compound as the first negative electrode active material, and by using a titanium-containing oxide that maintains structural stability during repeated charge and discharge with the second negative electrode active material. There is an effect that the cycle (cycle) characteristics are improved.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (16)

A first negative electrode mixture layer comprising a first negative electrode active material applied in contact with a surface of a current collector; And
A second negative electrode mixture layer coated on the first negative electrode mixture layer, the second negative electrode mixture layer comprising a second negative electrode active material having a relatively higher charge / discharge potential and a relatively higher hydrophilicity than the first negative electrode active material;
A secondary battery negative electrode comprising a multi-layer structure comprising a. The negative electrode of claim 1, wherein the affinity of the second negative electrode active material for the electrolyte is 20 to 300% greater than that of the first negative electrode active material. The method of claim 1, wherein the impregnation rate of the electrolyte solution to the second negative electrode mixture layer is a secondary battery negative electrode, characterized in that 30 to 200% greater than the first negative electrode active material. The negative electrode of claim 1, wherein the first negative electrode active material is at least one selected from the group consisting of crystalline graphite and low crystalline carbon. The negative electrode of claim 1, wherein the first negative electrode active material is coated with low crystalline carbon on a crystalline graphite core. The negative electrode for a secondary battery according to claim 4 or 5, wherein the first negative electrode active material is spherical. The negative electrode for a secondary battery according to claim 4 or 5, wherein the crystalline graphite is natural graphite or artificial graphite. The negative electrode of claim 4 or 5, wherein the low crystalline carbon is hard carbon or soft carbon. The negative electrode for a secondary battery according to claim 1, wherein the second negative electrode active material is a titanium-containing oxide. The anode of claim 9, wherein the titanium-containing oxide is at least one selected from the group consisting of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) and titanium dioxide (TiO ₂ ). The method according to claim 10, wherein when the second negative electrode active material is made of a mixture of lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ ) and titanium dioxide (TiO ₂ ), the content ratio thereof is 10:90 to 90 based on the weight ratio. A secondary battery negative electrode, characterized in that the range of: 10. Comprising a negative electrode according to claim 1, a positive electrode including at least one selected from the positive electrode active material for lithium secondary batteries represented by the formula (1) and formula (2), and a porous separator interposed between the negative electrode and the positive electrode Electrode assembly for secondary battery, characterized in that
Li _x (Ni _v Mn _w Co _y M _z ) O _2-t A _t (1)
In this formula,
0.8 <x ≦ 1.3, 0 ≦ v ≦ 0.9, 0 ≦ w ≦ 0.9, 0 ≦ y ≦ 0.9, 0 ≦ z ≦ 0.9, x + v + w + y + z = 2, 0 ≦ t <0.2;
M is at least one metal or transition metal cation of +2 to + 4-valent oxidation number
A is a -1 or -divalent anion.
Li _a Mn _2-b M ' _b 0 _4-c A' _c (2)
In this formula,
0.8 <a ≦ 1.3, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.3;
M 'is at least one metal or transition metal cation of +2 to + 4-valent oxidation number and A' is -1 or -divalent anion. A lithium secondary battery comprising the electrode assembly of claim 12. A battery module comprising the lithium secondary battery of claim 13 as a unit cell. An electric vehicle or a hybrid electric vehicle, characterized by using the battery module according to claim 14 as a power source. A power storage device characterized by using the battery module according to claim 14 as a power source.