WO2019088805A2 - Lithium manganese positive electrode active material having spinel structure, and positive electrode and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to a lithium manganese positive electrode active material having a spinel structure, a positive electrode and a lithium secondary battery comprising same, the lithium manganese positive electrode active material comprising: lithium manganese oxide represented by chemical formula [1] below; and a coating layer which is positioned on the surface of the lithium manganese oxide and comprises one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S, and thus showing excellent high-temperature storage characteristics. Chemical formula [1]: Li1+aMn2-bM1 bO4-cAc (In chemical formula [1], M1 is one or more metal elements comprising Li, A is one or more elements selected from the group consisting of F, Cl, Br, I, At and S, 0≤a≤0.2, 0<b≤0.5, and 0≤c≤0.1.)

Description

A lithium manganese-based cathode active material having a spinel structure, a positive electrode containing the lithium manganese-

Mutual citation with related application

This application claims the benefit of priority under Korean Patent Application No. 2017-0146924, dated November 6, 2017, and Korean Patent Application No. 2018-0135102, dated November 6, 2018, The contents of which are incorporated herein by reference.

Technical field

The present invention relates to a cathode active material for a lithium secondary battery, a cathode including the cathode active material, and a lithium secondary battery. More specifically, the present invention relates to a lithium manganese-based cathode active material having a spinel structure, which is excellent in high-temperature storage characteristics and high-temperature lifetime characteristics by improving Mn elution, and a positive electrode and a lithium secondary battery comprising the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density and voltage, a long cycle life, and a low self-discharge rate are commercially available and widely used.

Lithium transition metal composite oxides are used as the positive electrode active material of lithium secondary batteries. Among them, LiCoO ₂ Lithium cobalt composite metal oxide is mainly used. However, LiCoO ₂ has a poor thermal characteristic due to destabilization of crystal structure due to depolythium, and is expensive, so that it can not be used as a power source in fields such as electric vehicles.

Lithium manganese oxide (LiMnO ₂ or LiMn ₂ O ₄ ), lithium iron phosphate compound (LiFePO ₄ or the like) or lithium nickel composite metal oxide (LiNiO ₂ or the like) and the like have been developed as materials for replacing LiCoO ₂ . Among them, the lithium manganese oxide has an advantage of being excellent in thermal stability and output characteristics and being inexpensive. However, due to the Mn ^{3 +} , a structural distortion (Jahn-Teller distortion) occurs during charging and discharging, There is a problem in that the Mn elution occurs due to HF formed by the HF and the performance deteriorates abruptly.

Therefore, development of a cathode active material capable of suppressing Mn elution of the lithium manganese-based oxide and producing a secondary battery excellent in high-temperature characteristics at low cost is required.

In order to solve the above-described problems, a first technical object of the present invention is to provide a lithium manganese-based cathode active material having a spinel structure which is excellent in high-temperature storage characteristics and high-temperature lifetime characteristics by inhibiting elution of Mn.

A second technical object of the present invention is to provide a positive electrode for a lithium secondary battery which can realize excellent storage characteristics and lifetime characteristics at a high temperature by including the positive electrode active material.

A third object of the present invention is to provide a lithium secondary battery including the positive electrode according to the present invention and having excellent high-temperature storage characteristics and high-temperature lifetime characteristics.

The present invention relates to a lithium manganese oxide represented by the following formula (1); And a lithium manganese oxide which is located on the surface of the lithium manganese oxide and contains Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, And a coating layer comprising at least one coating element selected from the group consisting of Bi, Si, and S. The present invention also provides a lithium manganese-based cathode active material having a spinel structure.

[Chemical Formula 1]

Li _{1 + a} Mn _{2 - b} M ¹ _b O _{4 - ca c}

Wherein M ¹ is at least one metal element containing Li and A is at least one element selected from the group consisting of F, Cl, Br, I, At and S, and 0? A? 0.2, 0 < b? 0.5, 0? C? 0.1)

The present invention also provides a cathode comprising a cathode current collector and a cathode active material layer formed on the cathode current collector, wherein the cathode active material layer comprises the lithium manganese cathode active material of the spinel structure according to the present invention will be.

Further, there is provided a lithium secondary battery comprising a positive electrode according to the present invention.

According to the present invention, the structural stability can be improved by doping a lithium manganese-based cathode active material having a spinel structure with a doping element.

Further, by forming a coating layer on the surface of the lithium manganese-based cathode active material having the spinel structure, the contact between the electrolyte and the cathode active material is minimized, so that manganese elution is suppressed at a high temperature, thereby exhibiting high-temperature storage characteristics and high- .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a capacity and a resistance characteristic according to a cycle at a high temperature (45.degree. C.) of the secondary battery manufactured in Examples 1 to 5 and Comparative Examples 1 to 3 of the present invention.

2 is a graph showing capacitance and resistance characteristics at the time of high temperature (60 ° C) storage of the secondary batteries manufactured in Examples 1 to 5 and Comparative Examples 1 to 3 of the present invention.

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

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor can properly define the concept of the term to describe its invention in the best possible way And should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention.

In the present specification, the average particle diameter (D ₅₀ ) is defined herein as the particle diameter at the 50% reference of the particle diameter distribution and the average particle diameter (D ₅₀ ) is measured using a laser diffraction method . Specifically, the average particle diameter (D ₅₀ ) was measured by dispersing the target particles in a dispersion medium, introducing the particles into a commercially available laser diffraction particle size analyzer (for example, Microtrac MT 3000), irradiating ultrasound at about 28 kHz at an output of 60 W , It is possible to calculate the average particle size (D ₅₀ ) at the 50% reference of the cumulative distribution of the particle volume according to the particle size in the measuring apparatus.

In this specification, ICP analysis was conducted using an inductively coupled plasma emission spectrometer (ICP-OES; Optima 7300DV, PerkinElmer).

In the present specification, the " specific surface area " is measured by the BET method. Specifically, it can be calculated from the adsorption amount of nitrogen gas under the liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan.

In the present specification, "%" means weight% unless otherwise specified.

Cathode active material

First, a lithium manganese-based cathode active material having a spinel structure according to the present invention will be described.

The lithium manganese-based cathode active material of the present invention is a spinel-type cathode active material comprising a lithium manganese oxide represented by the following general formula (1) and a coating layer disposed on the surface of the lithium manganese oxide.

[Chemical Formula 1]

Li _{1 + a} Mn _{2 - b} M ¹ _b O _{4 - ca c}

In Formula 1, M ¹ is a doping element substituted for a manganese site in the lithium manganese oxide, and may be one or more metal elements including Li. The A is an element substituted for an oxygen site in the lithium oxynitride, and may be at least one element selected from the group consisting of F, Cl, Br, I, At and S.

Meanwhile, 1 + a represents the molar ratio of lithium in the lithium manganese oxide, and may be 0? A? 0.2, preferably 0? A? 0.1.

B represents the molar ratio of the doping element M ^{1 in} the lithium manganese oxide, and may be 0 < b? 0.5, preferably 0.03? B? 0.25. When the molar ratio b of M ¹ satisfies the above range, a structurally stable cathode active material can be obtained while minimizing the capacity drop.

C represents the molar ratio of the element A in the lithium manganese oxide, and may be 0? C? 0.1, preferably 0.01? C? 0.05.

The lithium manganese oxide represented by Formula 1 is doped with a doping element M ¹ having a lower oxidation number than Mn.

The lithium manganese oxide is doped with a doping element M ¹ having a lower oxidation number than that of Mn, thereby increasing the average oxidation number of Mn ions, resulting in a disproportionation reaction of Mn ions on the electrode surface (2Mn ³⁺ = Mn ^{2 +} + Mn ⁴ by reducing the Mn ^{+ 2} it is generated by the ^+), to inhibit the reaction between the HF generated in the electrolytic solution can be inhibited Mn dissolution.

In the present invention, when the lithium manganese oxide is doped with an element having the same oxidation number as Mn or having an oxidation number higher than that of Mn, the average oxidation number of the Mn ion is decreased and the Mn ^{2 +} Is increased. At this time, the generated Mn ^{2 +} is dissolved in the electrolyte and then reduced at the time of charging / discharging and deposited on the surface of the negative electrode, which may affect the cell performance such as capacity degradation.

The doping element M ¹ may be ^{one or more} of Al, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au, and Si. &Lt; RTI ID = 0.0 &gt; [0050] &lt; / RTI &gt; Preferably, M ¹ includes Li, and may further include at least one metal element selected from the group consisting of Al and Mg.

Preferably, the lithium manganese oxide may be represented by the following formula (1).

[Chemical Formula 1]

_{Li 1 + a Mn 2-b} Li b1 M a b2 O 4-c A c

Wherein M ^a is at least one metal element selected from the group consisting of Al and Mg, 0? A? 0.2, 0 <b1 + b2? 0.5, 0? C? 0.1, 0? B1 / b2? being.

As shown in Formula 1, preferably, the doping element M ¹ may include a metal element represented by Li and M ^a . Here, b1 represents a molar ratio of Li as a doping element in the lithium manganese oxide, and b2 represents a molar ratio of a metal element that can be additionally doped in addition to Li in the lithium manganese oxide. The b1 + b2 will represent the molar ratio of the doping element M ¹ in the lithium manganese oxide, and may be 0 <b≤0.5, preferably 0.03≤b≤0.25. The molar ratio of b1 / b2 may be 0? B1 / b2? 1.3, preferably 0.5? B1 / b2? 1.2. When the doping element M ¹ molar ratio of b1 and b2 containing the Li and M ^a to satisfy the above range, it is possible to obtain a stable cathode active material while minimizing the structural capacity decreases.

Next, the coating layer prevents contact between the lithium manganese oxide and the electrolytic solution to prevent generation of gas upon charge and discharge, and prevents manganese (Mn) from leaching at a high temperature. The coating layer is located on the surface of the lithium manganese oxide and contains at least one of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, (Hereinafter referred to as &quot; coating element &quot;) selected from the group consisting of Sb, Bi, Si, Preferably, the coating layer may include at least one element selected from the group consisting of W, Mg, B and Ti, and more preferably at least one element selected from the group consisting of W and B .

According to one embodiment, the lithium manganese-based cathode active material according to the present invention may be one in which the doping element M ¹ is at least one metal element including Li, Al and Mg, and the coating layer contains WO ₃ .

According to another embodiment, the lithium manganese based cathode active material according to the present invention may be one in which the doping element M ¹ is at least one metal element including Li, Al and Mg, and the coating layer contains B ₂ O ₃ .

According to another embodiment, the lithium manganese-based cathode active material according to the present invention may be one in which the doping element M ¹ is at least one metal element including Li, Al and Mg, and the coating layer comprises TiO ₂ .

According to another embodiment, the lithium manganese-based cathode active material according to the present invention may be one in which the doping element M ¹ is at least one metal element including Li, Al and Mg, and the coating layer contains MgO ₂ .

Meanwhile, the lithium manganese-based cathode active material having a spinel structure according to the present invention may include a lithium boron composite oxide and a lithium tungsten composite oxide.

For example, the lithium manganese-based cathode active material of the spinel structure may have a lithium-boron composite oxide and a lithium-tungsten composite oxide on the surface of the lithium manganese-based cathode active material. Preferably, the lithium manganese-based cathode active material may have secondary particles, and more preferably lithium-boron composite oxide and lithium tungsten composite oxide may exist on the surface and inside of the secondary particle.

The lithium boron complex oxide may be preferably lithium borate, more preferably lithium borate, lithium tetraborate, lithium pentaborate, and most preferably Li ₂ B ₄ O ₇ .

The lithium tungsten composite oxide may preferably be lithium tungstate, and most preferably Li ₂ WO ₄ .

For example, in the production of a lithium manganese-based cathode active material, boron raw material is mixed and fired in a raw material including a lithium raw material, a manganese raw material, and a tungsten raw material, and lithium boron oxide and lithium tungsten A complex oxide can be formed. The formation of the lithium-boron composite oxide and the lithium-tungsten composite oxide in the lithium manganese-based cathode active material can reduce the battery resistance and inhibit the elution of manganese during high-temperature storage.

On the other hand, the coating layer may be formed continuously or discontinuously on the surface of the lithium manganese oxide represented by Formula 1.

For example, the coating layer may be formed in an island shape in which particles including the coating elements are discontinuously adhered to the surface of the lithium manganese oxide. In this case, the particles including the coating elements may be, for example, WO ₃ , B ₂ O ₃ , ZnO, Al ₂ O ₃ , TiO ₂ , MgO, CaO, NbO ₂ , SrO, CrO, Mo ₂ O ₅ , Bi ₂ O ₃ , SiO, and the like. When the oxide particles are present on the surfaces of the lithium manganese oxide particles, the oxide particles capture and decompose HF formed by the reaction with the electrolyte, as shown in the following reaction formula 1, so that the Mn elution by HF is suppressed .

[Reaction Scheme 1]

ZnO + 2HF -> ZnF ₂ + H ₂ O

Al ₂ O ₃ + 6HF? 2AlF ₃ + 3H ₂ O

Alternatively, the coating layer may be formed in the form of a film containing the coating elements on the surface of the lithium manganese oxide. When the coating layer is formed in the form of a film, the effect of preventing the contact between the electrolyte and the lithium manganese oxide and the effect of inhibiting the manganese dissolution are more excellent. Preferably, the coating comprises at least one element selected from the group consisting of W, Mg, B and Ti. When the above-mentioned coating is formed on the surface of the lithium manganese oxide particles, contact with the electrolytic solution is blocked by the film, and side reactions and gas generation with the electrolyte can be suppressed.

On the other hand, the coating layer may be formed in a region corresponding to 50% to 100% of the total surface area of the lithium manganese oxide, preferably in a range of 80% to 100%, more preferably 90% to 100% . When the coating layer formation area satisfies the above range, the contact between the electrolytic solution and the lithium manganese oxide can be effectively blocked.

Further, the thickness of the coating layer may be 1 nm to 1000 nm, for example, 1 nm to 100 nm or 10 nm to 1000 nm. When the coating layer is formed in the form of a film, its thickness may be 1 nm to 100 nm, and when it is formed in the form of oxide particles, its thickness may be 10 nm to 1000 nm. When the thickness of the coating layer satisfies the above range, it is possible to effectively suppress occurrence of manganese elution and side reaction with the electrolyte while minimizing deterioration of electrical performance.

Meanwhile, the lithium manganese-based cathode active material of the present invention contains 500 to 40,000 ppm, preferably 2,500 to 40,000 ppm, and more preferably 3,000 to 40,000 ppm of the doping element M ¹ based on the total weight of the lithium manganese-based cathode active material can do. When the content of the doping element M ¹ satisfies the above range, the dissolution of manganese at a high temperature is effectively suppressed, thereby realizing a lithium secondary battery excellent in high-temperature storability.

According to one embodiment, the lithium manganese-based cathode active material may include Li or Li, Al and Mg, or a combination thereof as a doping element, wherein the Al is present in an amount of 2500 to 40000 ppm based on the total weight of the lithium manganese- Preferably 7,000 to 20,000 ppm, and the Li may be contained in an amount of 500 to 12,000 ppm, preferably 1000 to 3000 ppm, based on the total weight of the lithium manganese-based positive electrode active material. The Mg may be contained in an amount of 1000 to 20000 ppm, preferably 3000 to 10000 ppm based on the total weight of the lithium manganese-based cathode active material.

Meanwhile, the lithium manganese-based cathode active material according to the present invention has an average particle diameter (D ₅₀ ) of 1 to 20 μm, for example, 1 to 8 μm, 7 μm to 20 μm, 8 μm to 20 μm, Lt; / RTI &gt;

According to one embodiment, the lithium manganese-based cathode active material according to the present invention may have an average particle diameter (D ₅₀ ) of 1 to 8 μm. In the case of the lithium manganese-based cathode active material having a small average particle diameter (D ₅₀ ) as described above, the content of the doping and coating elements is relatively increased and the specific surface area is reduced by controlling the firing conditions and the like, A lithium manganese-based cathode active material having excellent structural stability and less side reaction with an electrolyte can be produced.

According to another embodiment, the lithium manganese-based cathode active material according to the present invention may have an average particle diameter (D ₅₀ ) of 8 to 20 탆. The lithium manganese-based cathode active material having a large average particle diameter (D ₅₀ ) as described above is advantageous in that manganese dissolution is relatively small as compared with particles having a small average particle diameter.

The lithium manganese-based active material may have a specific surface area of 0.1 to 1.5 m ² / g. The specific surface area may be adjusted according to the particle size of the lithium manganese based active material. For example, when the lithium manganese based active material is used as small particle size particles in a cathode material to be described later, the specific surface area is 0.5 to 1.5 m ² / g or 0.7 to 1.1 m ² / g, and when used as large diameter particles, the specific surface area may be 0.1 to 1 m ² / g or 0.25 to 0.7 m ² / g.

The lithium manganese-based cathode active material may be in the form of a secondary particle formed by aggregating primary particles or a plurality of primary particles. The secondary particles may be, for example, 2 to 100, or 2 to 50 primary particles formed.

Meanwhile, the lithium manganese-based cathode active material may include impurities that are not included in the manufacturing process. These impurities may include, for example, Fe, Ni, Na, Cu, Zn, Cr, Ca, K, S, Mg, Co, Si, B or combinations thereof. If such an impurity content is high, the life of the battery may be deteriorated by inducing the negative electrode dendrite, and a low voltage failure due to an internal short circuit may occur. Among these impurities, impurities such as S or the like have a problem of corroding the Al current collector. Therefore, it is preferable that the impurities are controlled to a certain degree or less.

For example, the lithium manganese-based cathode active material according to the present invention may have an S impurity content of 20000 ppm or less, preferably 15000 ppm or less, more preferably 1000 ppm or less, and the other impurity content may be 400 ppm or less, preferably 10 ppm or less have.

In the lithium manganese-based cathode active material according to the present invention, the total amount of magnetic impurities such as Fe, Cr, Ni, and Zn among the above-mentioned impurities is preferably not more than 800 ppb, specifically not more than 25 ppb. If the content of the magnetic impurities exceeds the above range, the life of the battery may be deteriorated by inducing the negative electrode dendrite, or a low voltage failure due to an internal short circuit may occur.

Method for producing cathode active material

Next, a method for producing the lithium manganese-based cathode active material according to the present invention will be described.

The lithium manganese-based cathode active material according to the present invention is characterized by comprising the steps of: forming a lithium manganese oxide doped with M ¹ represented by Formula 1; and mixing the lithium manganese oxide represented by Formula 1 with the coating raw material, To form a coating layer. Hereinafter, each step of the manufacturing method according to the present invention will be described in detail.

(1) to M1 Doped  Step of forming lithium manganese oxide

The lithium manganese oxide doped with M ¹ represented by Formula 1 may be prepared by mixing (i) a manganese raw material, a doping raw material containing M ¹ , and a lithium raw material, followed by sintering, or (ii) and reacting the doping raw material containing M ^1, it can be prepared by after the formation of the manganese precursor is doped with M ^1, method of sintering by mixing the manganese precursor and the lithium source material is doped with the above M ^1. That is, in the present invention, the doping element M ¹ may be added in the step of forming the manganese precursor, or may be charged in the step of firing the manganese raw material and the lithium raw material.

The manganese raw material may be a manganese element-containing oxide, a hydroxide, an oxyhydroxide, a carbonate, a sulfate, a halide, a sulfide, an acetate, a carboxylate or a combination thereof. Specific examples thereof include MnO ₂ , MnCl ₂ , MnCO ₃ , Mn ₃ O ₄ , MnSO ₄ , Mn ₂ O ₃ , Mn (NO ₃ ) ₂ , and the like, but is not limited thereto.

Doping material source material containing the M ¹ is, M ¹ containing oxides, hydroxides, oxy-hydroxides, sulfates, carbonates, halides, sulfides, acetates, and carboxylate, or the like combinations thereof, for example, Li (OH _{), LiCO 3, Li 2 O} , Al 2 (SO 4) 3, AlCl 3, Al- isopropoxide _{(Al-isopropoxide), AlNO 3} , MgO, Mg (OH) 2, MgSO 4, Mg (NO 3 ) _2, etc. However, the present invention is not limited thereto.

The lithium source material may be at least one selected from the group consisting of lithium containing carbonate (for example, lithium carbonate and the like), hydrate (for example, lithium hydroxide I hydrate (LiOH.H ₂ O) and the like), hydroxide (for example, For example, lithium nitrate (LiNO ₃ ) or the like), chloride (for example, lithium chloride (LiCl) or the like), and the like.

According to one embodiment, the lithium manganese oxide represented by Formula 1 may be prepared by mixing a manganese raw material, a doping raw material containing M ¹ , and a lithium raw material and then firing (Method (i)). .

The manganese raw material, the doping raw material including M ¹ , and the lithium raw material may be mixed in an amount that satisfies the molar ratio of Mn, M ^1, and Li in the formula (1).

In addition, the mixing may be a solid-phase mixing or a liquid-phase mixing. When the components are mixed through the solid-phase mixing, the firing process can be performed without a separate drying process. In the case of mixing the components through the liquid phase mixing, the mixed components are spray dried and then subjected to the firing process. When the solid-phase mixing method is used, a lithium manganese oxide having an average particle diameter (D ₅₀ ) of less than 8 μm, preferably not more than 6 μm, and having a small specific surface area can be obtained. On the other hand, when a wet mixing method is used, a lithium manganese oxide having an average particle diameter (D ₅₀ ) of 8 μm or larger can be obtained.

On the other hand, the firing may be performed at 600 to 900 ° C, preferably 700 to 800 ° C, for 5 to 24 hours, preferably 10 to 15 hours.

For example, the calcination may be performed at 750 to 850 캜, preferably at 780 to 830 캜 for 5 to 24 hours, preferably 10 to 15 hours. When the temperature and the firing time are satisfied, undersize occurs to increase the primary particle size. Accordingly, the average particle size (D ₅₀ ) of the primary particles is 1 μm or more, preferably 2 μm or more A lithium manganese oxide having a thickness of 3 m can be obtained.

According to other embodiments, the lithium manganese oxide represented by Formula 1, by reacting a doping raw material including a manganese raw material and M ^1, after the formation of the manganese precursor is doped with M ^1, doped with the M ¹ (Ii) mixing lithium manganese precursor with a lithium source material, followed by calcination.

Specifically, the manganese precursor doped to said M ¹ is, for example, be formed by co-precipitation reaction the doped raw material raw material containing manganese as a raw material M ^1. The manganese raw material and the doping raw material containing M &^lt; ¹ &gt; are the same as described above.

The coprecipitation reaction may be performed by a co-precipitation method well known in the art. For example, the manganese raw material and the doping element raw material are charged into the coprecipitation reactor at an appropriate ratio, and an aqueous ammonia solution as a complexing agent and an alkali And the reaction is allowed to proceed while the aqueous solution is added.

When a manganese precursor doped with M ¹ is generated through the above-mentioned coprecipitation reaction, the manganese precursor doped with M ¹ and the lithium source material are mixed and then fired to form lithium manganese oxide.

The manganese precursor doped with M ¹ and the lithium source material may be mixed in an amount that satisfies the molar ratio of Mn, M ^1, and Li in Formula 1.

On the other hand, the mixing and firing can be carried out in the same manner as described in method (i).

(2) Coating layer formation step

When the lithium manganese oxide doped with M ¹ represented by Formula 1 is prepared through the above process, the surface of the lithium manganese oxide of Formula 1 may be coated with Al, Ti, W, B, F, P, (Hereinafter referred to as "coating element") selected from the group consisting of Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, To form a coating layer.

For example, a wet coating method, a dry coating method, a plasma coating method, or an ALD (Atomic Layer Deposition) method can be used for forming the coating layer.

The wet coating method may be carried out by, for example, adding lithium manganese oxide and a coating material to an appropriate solvent such as ethanol, water, methanol, acetone, etc., and mixing the mixture until the solvent disappears.

The dry coating method is a method of mixing a lithium manganese oxide and a coating raw material in a solid phase without a solvent, and for example, a grinder mixing method, a mechanofusion method, or the like can be used.

The coating material may be at least one selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, , Oxides, hydroxides, carbonates, sulfates, halides, sulfides, acetates, carboxylates or combinations thereof, including at least one element selected from the group consisting of may be, for _{example, ZnO, Al 2 O 3,} Al (OH) 3, Al 2 (SO 4) 3, AlCl 3, Al- isopropoxide _{(Al-isopropoxide), AlNO 3} , TiO 2, WO _3, AlF, _{H 2 BO 3, HBO 2,} H 3 BO 3, H 2 B 4 O 7, B 2 O 3, C 6 H 5 B (OH) 2, (C 6 H 5 O) 3 B, (CH 3 (CH _{2) 3 O) 3 B,} C 3 H 9 B 3 O 6, (C 3 H 7 O 3) B, Li 3 WO 4, (NH 4) 10 W 12 O 41 · 5H 2 O, NH 4 H 2 PO ₄ , and the like.

After the coating material is adhered to the surface of the lithium manganese oxide through the above-described method, the coating layer can be formed through heat treatment. At this time, the heat treatment may be performed at 100 ° C to 700 ° C, preferably 300 ° C to 450 ° C, for 1 to 15 hours, preferably 3 to 8 hours.

anode

Next, a positive electrode for a lithium secondary battery according to the present invention will be described.

The positive electrode according to the present invention includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector. The positive electrode active material layer includes a lithium manganese-based positive electrode active material having a spinel structure, And optionally a conductive material and / or a binder.

Since the cathode active material is the same as that described above, a detailed description thereof will be omitted and only the remaining constitution will be specifically described below.

The cathode active material layer may further include a lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 below.

(2)

Li _{1 + x} [Ni _y Co _z Mn _w M ² _v ] O _{2 - p} B _p

M ² is a doping element substituted for a transition metal (Ni, Co, Mn) site, and W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, And at least one element selected from the group consisting of Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo. Preferably, the M ² may be at least one selected from the group consisting of Al, Zr, W, Ti, Nb and B.

The B is an oxygen-site-substituted element in the lithium nickel-manganese-cobalt cathode active material and may be at least one element selected from the group consisting of F, Cl, Br, I, At and S.

Meanwhile, 1 + x represents the lithium molar ratio in the lithium nickel-manganese-cobalt cathode active material, and may be 0? X? 0.3, preferably 0? X? 0.2, more preferably 0? X? .

Y represents the molar ratio of nickel in the lithium nickel-manganese-cobalt cathode active material and satisfies 0.5? Y <1, preferably 0.65? Y <1, more preferably 0.7? Y <1, Lt; y < 1.

Z represents the molar ratio of cobalt in the lithium nickel-manganese-cobalt cathode active material, and may be 0 <z <0.35, preferably 0 <z≤0.3.

The w represents the molar ratio of manganese in the lithium nickel-manganese-cobalt cathode active material, and may be 0 <w <0.35, preferably 0 <w? 0.3.

When the molar ratio y, z, and w of the transition metal in the lithium nickel-cobalt-manganese-based oxide satisfy the above range, a cathode active material having an excellent energy density can be obtained.

V represents the molar ratio of the doping element M ^{2 in} the lithium nickel-cobalt-manganese based oxide, and 0? V? 0.1, preferably 0.0005? V? 0.08, more preferably 0.001? V? 0.0 &gt; v &lt; / RTI &gt; When the molar ratio of the doping element M ^{2 in} the lithium nickel-cobalt-manganese oxide satisfies the above range, a cathode active material having excellent high-temperature stability can be obtained.

P represents the molar ratio of the element B in the lithium nickel-cobalt-manganese oxide, and may be 0? P? 0.1, preferably 0? P? 0.05.

More specifically, the lithium nickel-cobalt-manganese-based oxide represented by the above formula (2) is preferably Li _{1 + x} [Ni _y Co _z Mn _w ] O _{2 ,} Li _{1 + x} [Ni _y Co _z Mn _{w v} ] O ₂ , and the like, but is not limited thereto.

The lithium nickel-cobalt-manganese-based positive electrode active material represented by the above-mentioned Formula 2 is a lithium nickel-cobalt- At least one coating element selected from the group consisting of Mo, Sr, Sb, Bi, Si, and S may be further included. For example, the coating layer prevents contact between the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 and the electrolyte contained in the lithium secondary battery, thereby suppressing the occurrence of side reactions. And the filling density of the cathode active material can be increased.

As described above, when the coating element is additionally included, the content of the coating element in the coating layer is preferably from 100 ppm to 10,000 ppm, more preferably from 100 ppm to 10000 ppm with respect to the total weight of the lithium nickel-cobalt- 200 ppm to 5,000 ppm. For example, when the coating element is contained in the above range based on the total weight of the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2, the side reaction with the electrolyte is more effectively suppressed, The characteristics can be further improved.

The coating layer may be formed on the entire surface of the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2, or may be partially formed. Specifically, when the coating layer is partially formed on the surface of the lithium nickel-cobalt-manganese-based cathode active material represented by Chemical Formula 2, the total surface area of the lithium nickel-cobalt-manganese-based cathode active material represented by Chemical Formula 2 % To less than 100%, preferably 20% to less than 100%.

The average particle diameter (D ₅₀ ) of the lithium nickel-cobalt-manganese-based positive electrode active material represented by Formula 2 may be 1 μm to 20 μm, 2 μm to 10 μm, or 8 to 20 μm. When the average particle diameter (D ₅₀ ) of the lithium nickel-cobalt-manganese-based positive electrode active material represented by the above formula (2) satisfies the above range, excellent electrode density and energy density can be realized.

The crystal size of the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 may be 200 nm to 500 nm. When the grain size of the lithium nickel-cobalt-manganese-based positive electrode active material represented by the above formula (2) satisfies the above range, excellent electrode density and energy density can be realized.

On the other hand, the lithium nickel-cobalt-manganese-based cathode active material represented by the general formula (2) may have a constant content of transition metal elements in the active material particle regardless of its position, May be changing. For example, the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 may have a concentration gradient in which at least one of Ni, Mn, Co, and M ² gradually changes, Concentration gradient means that the concentration of the components is present in a concentration distribution in which the concentration of the components changes continuously or stepwise in all or a specific region of the particle.

On the other hand, the lithium nickel-cobalt-manganese-based cathode active material represented by the above-described formula (2) can be obtained by using a commercially available lithium nickel-cobalt-manganese-based cathode active material or by using a lithium nickel- And may be one produced by a manufacturing method.

For example, the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 may be prepared by mixing a nickel-cobalt-manganese-based precursor with a lithium source material, and optionally a doping source material, followed by firing.

The nickel-cobalt-manganese precursor may be a hydroxide of nickel-manganese-cobalt, a hydroxide, an oxide of hydroxide, a carbonate, an organic complex or a hydroxide of nickel-manganese-cobalt containing an element of doping M ² , . For example, the nickel-cobalt-manganese-based precursor may be selected from the group consisting of [Ni _y Co _z Mn _w ] (OH) ₂ , [Ni _y Co _z Mn _w Al _v ] (OH) _2, [Ni _y Co _z Mn _w ] O · OH, [Ni _y Co _z Mn _w Al _v ] O · OH, etc. However, the present invention is not limited thereto.

The lithium source material may be at least one selected from the group consisting of lithium-containing carbonate (for example, lithium carbonate and the like), hydrate (for example, lithium hydroxide I hydrate (LiOH.H ₂ O) For example, lithium nitrate (LiNO ₃ ) and the like), chlorides (e.g., lithium chloride (LiCl) and the like), and the like.

The doping material may be at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, , B, and Mo, or an oxide, a hydroxide, a sulfide, an oxyhydroxide, a halide, or a mixture thereof.

On the other hand, the firing may be performed at 600 to 1000 ° C, preferably 700 to 900 ° C for 5 to 30 hours, preferably 10 to 20 hours.

Meanwhile, when the lithium nickel-cobalt-manganese-based cathode active material represented by Formula 2 includes a coating layer, the coating raw material may be further added after the firing, followed by heat treatment.

The coating material may be selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, A hydroxide, an oxide hydroxide, a carbonate, a sulfate, a halide, a sulfide, an acetate, a carboxylate, or a combination thereof including at least one element selected from the group consisting of S , for _{example, ZnO, Al 2 O 3,} Al (OH) 3, Al 2 (SO 4) 3, AlCl 3, Al- isopropoxide _{(Al-isopropoxide), AlNO 3} , TiO 2, WO 3, AlF, _{H 2 BO 3, HBO 2,} H 3 BO 3, H 2 B 4 O 7, B 2 O 3, C 6 H 5 B (OH) 2, (C 6 H 5 O) 3 B, [(CH 3 ( _{CH 2) 3 O) 3 B} , C 3 H 9 B 3 O 6, (C 3 H 7 O 3) B, Li 3 WO 4, (NH 4) 10 W 12 O 41 · 5H 2 O, NH 4 H ₂ PO ₄ And the like, but is not limited thereto.

For example, a wet coating method, a dry coating method, a plasma coating method, or an ALD (Atomic Layer Deposition) method can be used for forming the coating layer.

The heat treatment may be performed at 100 ° C to 700 ° C, preferably 300 ° C to 450 ° C, for 1 to 15 hours, preferably 3 to 8 hours.

The lithium nickel-cobalt-manganese-based cathode active material represented by the general formula (2) represented by the general formula (2) is a high nickel cathode active material having a nickel ratio of more than 50 mol%, and is excellent in energy density characteristics. Therefore, when the lithium manganese-based cathode active material of Formula 2 is mixed with the lithium manganese-based cathode active material of the spinel structure of the present invention, the disadvantage of the lithium manganese-based positive electrode active material can be solved.

The positive electrode material comprising the lithium manganese-based positive electrode active material and the lithium nickel-cobalt-manganese-based positive electrode active material is characterized in that the large-diameter particles having an average particle diameter (D ₅₀ ) of 4 to 20 μm and an average particle diameter (D ₅₀ ) May have a bimodal particle diameter distribution including small particle size particles of 10% to 75%, preferably 25% to 75% of the average particle size (D ₅₀ ) of the hard particles. When a cathode material having a bimodal particle size distribution is used as described above, a cathode having a high electrode density and an energy density can be formed.

Preferably, the average particle diameter (D ₅₀ ) of the large diameter particles may be 8 탆 to 20 탆, 8 탆 to 15 탆, or 12 탆 to 20 탆, and the average particle diameter (D ₅₀ ) 1 탆 to 15 탆, 2 탆 to 13 탆, 2 탆 to 8 탆, or 4 탆 to 13 탆.

According to one embodiment, the cathode material according to the present invention may have a bimodal particle size distribution including large-diameter particles having an average particle diameter of 8 탆 to 15 탆 and small-particle particles having an average particle diameter of 1 탆 to 6 탆 .

According to another embodiment, the cathode material according to the present invention may have a bimodal particle diameter distribution including large-diameter particles having an average particle diameter of 12 to 20 μm and small-particle particles having an average particle diameter of 4 to 13 μm .

On the other hand, the kind of active material constituting the small particle size particles and large particle size particles is not particularly limited and may be the lithium manganese based active material and / or the lithium nickel-cobalt-manganese based active material.

According to one embodiment, the cathode material of the present invention may be such that the lithium manganese-based cathode active material constitutes large-diameter particles and the lithium nickel-cobalt-manganese-based cathode active material constitutes small particle size particles. In this case, the average particle size (D50) of the lithium manganese-based positive electrode active material is about 8 to 20 m, preferably about 12 to 20 m, and the average particle size (D50) of the lithium nickel- May be about 1 mu m to 15 mu m, preferably about 4 mu m to 13 mu m. In the case where large particle particles satisfying the above-described range are used as the lithium manganese-based cathode active material, the manganese elution in the lithium manganese-based cathode active material can be more effectively inhibited, and as a result, the high temperature stability of the battery can be further improved have.

According to another embodiment, the cathode material of the present invention may be such that the lithium manganese-based cathode active material forms small particle size particles and the lithium nickel-cobalt-manganese type cathode active material forms large particle particles. In this case, the average particle size (D50) of the lithium manganese-based cathode active material is about 1 to 15 m, preferably about 1 to 8 m, and the average particle size (D50) of the lithium nickel- 8 mu m to 20 mu m, and preferably about 8 mu m to 15 mu m. When the lithium manganese type cathode active material is used with small particle size satisfying the above range, it is possible to apply the doping and / or coating amount of the lithium manganese type cathode active material to a high level and to have a low BET value, Can be minimized.

According to another embodiment, the cathode material of the present invention is characterized in that at least one of the lithium manganese-based cathode active material and the lithium nickel-cobalt-manganese-based cathode active material has a bimodal particle size distribution including the large- .

Meanwhile, the cathode material may include the lithium manganese-based cathode active material and the lithium nickel-cobalt-manganese-based cathode active material at a weight ratio of 10:90 to 90:10, preferably 40:60 to 60:40. When the mixing ratio of the lithium manganese-based cathode active material to the lithium nickel-cobalt-manganese-based cathode active material satisfies the above range, an electrode excellent in high temperature storability and capacity characteristics can be obtained.

The positive electrode active material may be contained in an amount of 80 to 99 parts by weight, more specifically 85 to 98.5 parts by weight, based on 100 parts by weight of the total weight of the positive electrode active material layer. When included in the above content range, excellent capacity characteristics can be exhibited.

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

The conductive material is used for imparting conductivity to the electrode. The conductive material is not particularly limited as long as it has electron conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum and silver; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; And polyphenylene derivatives. These may be used alone or in admixture of two or more. The conductive material may be included in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

The binder serves to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose ), Starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, and various copolymers thereof. One kind or a mixture of two or more kinds of them may be used. The binder may be included in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

The positive electrode of the present invention can be produced by a conventional positive electrode manufacturing method, except that the lithium manganese-based positive electrode active material of the spinel structure described above is used. Specifically, the positive electrode active material and optionally the positive electrode mixture prepared by dissolving or dispersing the binder and / or the conductive material in a solvent may be coated on the positive electrode current collector, followed by drying and rolling.

Examples of the solvent include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and the like. Water and the like, and one kind or a mixture of two or more kinds can be used. It is sufficient that the amount of the solvent used can be adjusted so that the positive electrode mixture has an appropriate viscosity in consideration of the coating thickness of the slurry and the production yield.

Alternatively, the positive electrode may be produced by casting the positive electrode composite material on a separate support, and then peeling off the support from the support to laminate a film on the positive electrode collector.

Lithium secondary battery

Next, a lithium secondary battery according to the present invention will be described.

The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is the same as the positive electrode according to the present invention. Therefore, a detailed description of the positive electrode will be omitted and only the remaining configuration will be described below.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

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

The anode active material layer optionally includes a binder and a conductive material together with the anode active material.

As the negative electrode active material, various negative electrode active materials used in the related art can be used, and there is no particular limitation. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon; Metal compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and dedoping lithium such as SiO? (0 <? <2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Or a composite containing the metallic compound and the carbonaceous material such as Si-C composite or Sn-C composite, and any one or a mixture of two or more thereof may be used. Also, a metal lithium thin film may be used as the negative electrode active material. As the carbon material, both low crystalline carbon and highly crystalline carbon may be used. Examples of the low-crystalline carbon include soft carbon and hard carbon. Examples of the highly crystalline carbon include natural graphite, artificial graphite, artificial graphite or artificial graphite, Kish graphite graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar coke derived cokes).

On the other hand, in the lithium secondary battery of the present invention, it is preferable that a mixture of two or more kinds of carbon materials having specific specific surface area is used as the negative electrode active material.

For example, the negative electrode active material layer may include natural graphite and soft carbon, and more specifically, natural graphite having a specific surface area (BET) of 2.5 to 4.0 m ² / g and a specific surface area (BET ) Of 7 to 10 m &lt; ² &gt; / g. When the negative electrode comprising the natural graphite and the softened carbon satisfying the specific surface area ranges and the positive electrode according to the present invention are combined, the high temperature durability of the secondary battery can be further improved. If necessary, the anode active material layer may further include artificial graphite, and the artificial graphite may have a specific surface area (BET) of 0.1 to 1.2 m ² / g.

More desirably, the negative electrode active material layer may comprise from 70 to 95% by weight of natural graphite, from 0 to 25% by weight of artificial graphite and from 5 to 30% by weight of soft carbon, based on the total weight of the negative electrode active material have.

Alternatively, the negative electrode active material layer may include natural graphite and artificial graphite. Specifically, natural graphite having a specific surface area (BET) of 2.5 to 4.0 m ² / g and a graphite having a specific surface area (BET) of 0.1 to 1.2 m ² / g of artificial graphite. If necessary, the negative active material layer may further include soft carbon. In this case, the soft carbon may have a specific surface area (BET) of 7 to 10 m ² / g. More desirably, the negative electrode active material layer may comprise 10 to 50% by weight of natural graphite, 50 to 90% by weight of artificial graphite and 0 to 20% by weight of soft carbon based on the total weight of the negative electrode active material have. In this case, the cathode rate can be improved and a battery having excellent cell fast charging and resistance characteristics can be realized.

On the other hand, the negative electrode active material may include 80% by weight to 99% by weight based on the total weight of the negative electrode active material layer.

The binder is a component for assisting the bonding between the conductive material, the active material and the current collector, and is usually added in an amount of 0.1% by weight to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene Examples thereof include ethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluorine rubber and various copolymers thereof.

The conductive material may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer, as a component for further improving the conductivity of the negative electrode 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 acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The negative electrode active material layer is prepared by applying and drying a composition for forming a negative electrode active material layer which is prepared by dissolving or dispersing a negative electrode active material on a negative electrode current collector and optionally a binder and a conductive material in a solvent and drying the composition for forming the negative electrode active material layer Casting the composition on a separate support, and then peeling the support from the support to laminate a film on the negative electrode collector.

Meanwhile, the negative electrode active material layer may have a single layer structure or a multi-layer structure in which two or more layers are stacked. For example, the negative electrode may include a negative electrode collector, a first negative electrode active material layer formed on the negative electrode collector, and a second negative electrode active material layer formed on the first negative electrode active material layer, The active material layer and the second negative electrode active material layer may have different compositions.

For example, the first negative electrode active material layer may contain 5 to 100% by weight, preferably 80 to 100% by weight, of natural graphite among all the negative electrode active materials contained in the first negative electrode active material layer, The negative electrode active material layer may contain 15 to 95% by weight, preferably 15 to 65% by weight, of softened carbon among all the negative electrode active materials contained in the second negative electrode active material layer. When the structural anode is used, the improvement of the electrode adhesion improves the processability, and it is possible to produce a battery having excellent rapid charging performance and resistance performance and excellent high temperature storage characteristics.

On the other hand, the loading amount of the negative electrode may be 300 to 500 mg / 25 cm ² , preferably 300 to 400 mg / 25 cm ² . When the loading amount of the negative electrode satisfies the above range, it is possible to secure a sufficient electrode bonding force, to facilitate a process, to realize a battery having excellent rapid charging performance and resistance performance, and to maximize energy density.

Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode to provide a passage for lithium ion, and can be used without any particular limitation as long as it is used as a separator in a lithium secondary battery. Particularly, It is preferable that the electrolyte membrane has a low resistance to water and an excellent ability to impregnate electrolytes. Specifically, porous polymer films such as porous polymer films made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers, May be used. Further, a nonwoven fabric made of a conventional porous nonwoven fabric, for example, glass fiber of high melting point, polyethylene terephthalate fiber, or the like may be used. In order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and the separator may be selectively used as a single layer or a multilayer structure.

As the electrolyte used in the present invention, there can be used an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte which can be used for a lithium secondary battery, .

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

The organic solvent may be used without limitation as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate,? -Butyrolactone and? -Caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethyl carbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate PC) and the like; Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Ra-CN (Ra is a linear, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among these, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant, for example, such as ethylene carbonate or propylene carbonate, For example, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1: 1 to 9, the performance of the electrolytic solution may be excellent.

The lithium salt may be used, without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as an anion, and containing the Li ⁺ in the lithium salt cation is F ^-, Cl ^-, Br ^-, I ^-, NO _{^{3 -, N (CN) 2}} -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF 6 -, BF 2 C 2 O 4 -, BC 4 O 8 _{^{-, PF 4 C 2 O 4}} -, PF 2 C 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 _{^{PF -, (CF 3) 6}} P -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N - _{, CF 3 CF 2 (CF 3} ) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- . Specifically, the lithium salt may be LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , LiAlO ₄ , and LiCH ₃ SO ₃ , or a mixture of two or more thereof.

The lithium salt can be appropriately changed within a range that is usually usable, but it can be specifically contained in the electrolyte in an amount of 0.8 M to 3 M, specifically 0.1 M to 2.5 M.

In addition to the electrolyte components, various additives may be added to the electrolyte for the purpose of improving lifetime characteristics of the battery, suppressing the reduction of the battery capacity, and improving the discharge capacity of the battery.

Further, the electrolyte may further include an additive, if necessary. Such additives include, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate and the like; N, N &lt; RTI ID = 0.0 &gt; (N, &lt; / RTI &gt; N, N'-tetramethyluronium hexafluorophosphate), pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, Substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride, and the above additives may be used singly or in combination. The additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

The lithium secondary battery according to the present invention can be used for portable equipment such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEV).

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

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

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

The lithium secondary battery according to the present invention can be used not only in a battery cell used as a power source of a small device but also as a unit cell in a middle- or large-sized battery module including a plurality of battery cells.

Hereinafter, the present invention will be described in detail by way of examples with reference to the following examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Manufacturing example  One

MnSO ₄ And Li ₂ CO ₃ were mixed at a weight ratio of 99: 1, and then MnSO ₄ .7H ₂ O containing Li ₂ CO ₃ having a concentration of 2M was prepared using distilled water subjected to N ₂ purging. MnSO ₄ .7H ₂ O containing Li ₂ CO ₃ was added to the continuous stirred tank reactor (CSTR, manufactured by EMS Tech, product name: CSTR-L0) at a rate of 250 mL / h. A 40% aqueous solution of sodium hydroxide was introduced as an alkalizing agent at a rate of 10 mL / h through an aqueous solution of sodium hydroxide in the reactor, and a 25% ammonia solution was fed through the ammonia solution supply portion of the reactor at a rate of 30 mL / And the pH of the solution was maintained at 10.5. The temperature of the reactor was adjusted to 40 캜, the retention time (RT) was adjusted to 10 hours, and the mixture was stirred at a speed of 1200 rpm to precipitate Mn ₃ O ₄ containing Li. The obtained reaction solution was filtered through a filter, purified by distilled water and then dried to prepare a Li-doped manganese precursor (Mn _0.96 Li _0.04 ) ₃ O ₄ .

The Li-doped manganese precursor thus prepared was mixed with lithium raw material Li ₂ CO ₃ at a molar ratio of 1: 0.75 and then calcined at 810 ° C for 14 hours to obtain lithium manganese oxide Li _1.0 (Mn _1.92 Li _0.08 ) O ₄ .

Manufacturing example  2

MnSO _4, a doping element Li ₂ CO ₃ and Al ₂ (SO _{4) 3} to 95: _0.5: 4.5 is used in a weight ratio of Li and Al doped with manganese precursor (Mn Li _{0 .957 0 0 028 015} Al ) ₃ O ₄ .

The same procedure as in Preparation Example 1 was carried out except that the lithium manganese oxide Li (Mn _1.914 Li _0.06 Al _0.056 ) O ₄ was prepared by mixing and firing the Li and Al-doped manganese precursor thus prepared with the lithium source material Respectively.

Manufacturing example  3

MnSO _4, doping elements as Li ₂ CO ₃ and MgSO ₄ to 98: 0.5: 1.5 was used in a weight ratio of Li and Mg doped with manganese precursor _{(.. Mn 0 .961 Li 0} 021 Mg 0 018) to ₃ O ₄ .

The same procedure as in Preparation Example 1 was _conducted except that lithium manganese oxide Li (Mn _1.922 Li _0.042 Mg _0.036 ) O ₄ was prepared by mixing and firing the Li and Mg-doped manganese precursor thus prepared and the lithium raw material Respectively.

Manufacturing example  4

MnSO _4, a doping element _{Li 2 CO 3, Al 2 (} SO 4) 3 , and MgSO ₄ to 96.4: 0.5: 2.3: using a weight ratio of 0.8 Li, Al and Mg-doped manganese precursor (Mn _{0 96} Li _{0. . 02 Al 0. 01 Mg 0} . 01) was prepared in a ₃ O _4.

Prepared as described above, Li, Al, Mg and the lithium manganese oxide by mixing and firing the doped manganese precursor with a lithium raw material _{Li (Mn 1. 92 Li 0} . 04 Al 0. 02 Mg 0. 02) producing a ₃ O ₄ The procedure of Preparation Example 1 was repeated,

Manufacturing example  5

A Mg-doped manganese precursor (Mn _0.96 Mg _0.04 ) ₃ O ₄ was prepared using MgSO ₄ instead of Li ₂ CO ₃ as the doping element.

The Mg-doped manganese precursor prepared as described above and the lithium source material were mixed and fired to obtain lithium manganese oxide Li _{1 . 0} (Mn _1.92 Mg _0.08 ) O ₄ was prepared in the same manner as in Production Example 1.

Manufacturing example  6

As doping element use the Li ₂ CO ₃ instead of Al ₂ (SO _{4) 3,} it was prepared in the Al-doped manganese precursor _{(Mn 0.96 Al 0.04) 3 O} 4.

The thus prepared Al-doped manganese precursor and the lithium raw material were mixed and fired to obtain lithium manganese oxide Li _{1 . 0} &lt; / RTI &gt; (Mn _1.92 Al _0.08 ) O ₄ was prepared.

Example  One

5,000 ppm of WO ₃ was added to 100 parts by weight of the lithium manganese oxide prepared in Preparation Example 1, and the mixture was heat-treated at 600 ° C for 5 hours to obtain a lithium manganese cathode active material A having a coating layer containing W.

A positive electrode active material A, a carbon black conductive material and a PVdF binder were mixed in a N-methylpyrrolidone solvent in a weight ratio of 95: 2.5: 2.5 to prepare a positive electrode mixture, which was then applied to an aluminum current collector, Dried, and rolled to prepare a positive electrode, and the positive electrode was used to prepare a coin cell.

Example  2

A coin cell was prepared in the same manner as in Example 1 except that 3,000 ppm of H ₃ BO ₃ was added to 100 parts by weight of the lithium manganese oxide prepared in Preparation Example 1 and mixed.

Example  3

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Preparation Example 2 was used as a cathode active material.

Example  4

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Preparation Example 3 was used as a cathode active material.

Example  5

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Preparation Example 4 was used as a cathode active material.

Comparative Example  One

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Production Example 1 was used as a cathode active material.

Comparative Example  2

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Preparation Example 5 was used.

Comparative Example  3

A coin cell was prepared in the same manner as in Example 1, except that the lithium manganese oxide prepared in Preparation Example 6 was used.

Experimental Example  1: Manganese dissolution experiment

The amounts of manganese leached out from the coin cells prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured. Specifically, the coin cell was charged and discharged once, and then discharged to 3.0 V. Subsequently, the coin cell was disassembled, kept in a sealed container for 4 weeks in 4 mL of the electrolyte, and the amount of dissolved Mn in the electrolyte solution was measured by ICP analysis. The electrolyte solution was prepared by dissolving 1 M of LiPF ₆ in an organic solvent prepared by mixing ethylene carbonate: dimethyl carbonate: diethyl carbonate in a volume ratio of 1: 2: 1, and mixing 2% by weight of vinylene carbonate.

The measurement results are shown in Table 1 below.

	Manganese elution (ppm)
Example 1	40
Example 2	76
Example 3	65
Example 4	60
Example 5	63
Comparative Example 1	128
Comparative Example 2	125
Comparative Example 3	83

As shown in Table 1, the amounts of manganese elution of the lithium manganese oxides prepared in Examples 1 to 5 were significantly smaller than those of Comparative Examples 1 to 3.

Experimental Example 2: High Temperature Life Characteristic

The lifespan characteristics of the coin cells prepared in Examples 1 to 5 and Comparative Examples 1 to 3 at high temperatures were measured.

Specifically, each of the lithium secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was charged at a constant current of 1 C at a temperature of 45 ° C to 4.3 V at a cut off of 0.05C. Then, discharging was performed until the voltage reached 3 V with a constant current of 1C.

The above charging and discharging behaviors were repeated one cycle, and these cycles were repeated 200 times. The high temperature (45 ° C) lifetime characteristics according to Examples 1 to 5 and Comparative Examples 1 to 3 were measured, Respectively.

	Capacity retention rate (%)	Rate of resistance increase (%)
Example 1	92.3	148
Example 2	83.5	198
Example 3	80.3	188
Example 4	82.7	183
Example 5	81.4	185
Comparative Example 1	69.2	245
Comparative Example 2	71.2	239
Comparative Example 3	79.2	215

As shown in Table 2 and FIG. 1, in the case of the coin cell comprising the lithium manganese-based cathode active material of the spinel structure prepared in Examples 1 to 5, the lithium manganese-based cathode active material prepared in Comparative Examples 1 to 3 It was confirmed that the capacity retention ratio and the rate of resistance increase according to the cycle were remarkably excellent at a high temperature as compared with the coin cell.

Experimental Example 3: High-temperature storage characteristics

The storage characteristics of the coin cells prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured at high temperature.

Specifically, the coin cells prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were fully charged to 4.3 V, and then stored at 60 占 폚 for 4 weeks. The coin cell was charged to 4.3 V with a constant current of 0.1 C and then discharged to 3.0 V with a constant current of 0.1 C and the discharge capacity and resistance at that time were measured. And Fig.

	Capacity retention rate (%)	Rate of resistance increase (%)
Example 1	90.3	167
Example 2	77.6	224
Example 3	80.8	199
Example 4	85.3	189
Example 5	82.1	194
Comparative Example 1	65.8	267
Comparative Example 2	70.1	254
Comparative Example 3	75.1	234

As shown in Table 3 and FIG. 2, in the case of the coin cell comprising the lithium manganese-based cathode active material of the spinel structure prepared in Examples 1 to 5, the lithium manganese-based cathode active material prepared in Comparative Examples 1 to 3 (60 ℃) for 4 weeks compared with coin cells.

Claims (14)

1. A lithium manganese oxide represented by the following formula (1); And

   The lithium manganese oxide may be at least one selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, And a coating layer containing at least one coating element selected from the group consisting of Si, S, and S. A lithium manganese-based cathode active material having a spinel structure.

   [Chemical Formula 1]

   Li _{1 + a} Mn _{2 - b} M ¹ _b O _{4 - ca c}

   In Formula 1,

   M ¹ is at least one metal element containing Li and A is at least one element selected from the group consisting of F, Cl, Br, I, At and S, 0? A? 0.2, 0 <b? 0.5, 0? C? 0.1.
2. The method according to claim 1,

   The doping element M ¹ may be at least ^{one selected} from the group consisting of Al, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Wherein the lithium manganese-based positive electrode active material further comprises at least one metallic element selected from the group consisting of Si and Si.
3. The method according to claim 1,

   Wherein the doping element M &^lt; ¹ &gt; further comprises at least one metal element selected from the group consisting of Al and Mg.
4. The method according to claim 1,

   Wherein the lithium manganese oxide is represented by the following formula (1).

   [Chemical Formula 1]

   _{Li 1 + a Mn 2-b} Li b1 M a b2 O 4-c A c

   Wherein M ^a is at least one metal element selected from the group consisting of Al and Mg, 0? A? 0.2, 0 <b1 + b2? 0.5, 0? C? 0.1, 0? B1 / b2? being.
5. The method according to claim 1,

   Wherein the coating layer comprises at least one selected from the group consisting of Mg, Ti, B, and W. The lithium manganese-based cathode active material of claim 1,
6. The method according to claim 1,

   Wherein the coating layer has a spinel structure having a thickness of 1 nm to 1,000 nm.
7. The method according to claim 1,

   The lithium manganese-based cathode active material has a spinel structure having an average particle diameter (D ₅₀ ) of 1 탆 to 20 탆.
8. The method according to claim 1,

   The lithium manganese-based cathode active material has a spinel structure having a specific surface area of 0.1 to 1.5 m ² / g.
9. The method according to claim 1,

   The lithium manganese-based cathode active material is a lithium manganese-based cathode active material having a spinel structure in the form of a secondary particle formed by aggregating primary particles or a plurality of primary particles.
10. 10. The method of claim 9,

    Wherein the secondary particles are formed from 2 to 50 primary particles.
11. 3. The method of claim 2,

    The lithium manganese-based cathode active material of the spinel structure includes a lithium-boron composite oxide and a lithium-tungsten composite oxide.
12. A positive electrode collector, and a positive electrode active material layer formed on the positive electrode collector,

    Wherein the cathode active material layer comprises a lithium manganese-based cathode active material having a spinel structure according to any one of claims 1 to 11.
13. 13. The method of claim 12,

    Wherein the cathode active material layer further comprises a lithium nickel-cobalt-manganese-based cathode active material represented by the following formula (2).

    (2)

    Li _{1 + x} [Ni _y Co _z Mn _w M ² _v ] O _{2 - p} B _p

    In Formula 2, M ² is at least one element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, B, at least one element selected from the group consisting of Nb, Mg, B and Mo; B is at least one element selected from the group consisting of F, Cl, Br, I, At and S; 0.50? Y <1, 0 <z <0.35, 0 <w <0.35, 0? V? 0.1, 0? P?
14. A lithium secondary battery comprising the positive electrode according to claim 12.

Images