KR101986163B1 - A transition metal composite precursor and cathode materials for secondary battery - Google Patents

Abstract

The present invention relates to a transition metal complex compound precursor which can be used as a material for a cathode active material of a secondary battery and a method for producing the same. And more particularly, to a transition metal complex compound precursor capable of realizing high stability, excellent charge / discharge capacity and life characteristics, a method for producing the same, and a cathode active material for a lithium secondary battery obtained from the transition metal complex compound precursor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transition metal complex compound precursor containing manganese and a cathode active material for a secondary battery comprising the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a transition metal complex compound precursor containing manganese which can be used as a material for a cathode active material of a secondary battery and a method for producing the same. More particularly, the present invention relates to a transition metal complex compound precursor containing manganese which can realize high stability and excellent charge / discharge capacity and life characteristics, a process for producing the same, and a cathode active material for a lithium secondary battery obtained from the transition metal complex compound precursor will be.

Lithium secondary batteries are widely used as power sources for portable devices such as mobile phones, notebooks, and tablets due to the spread of portable devices. In recent years, not only these small electric and electronic devices, but also applications such as electric vehicles have been increasingly used.

A variety of cathode active materials have been developed for use in electric vehicles in mid- to large-sized batteries, but it is necessary to develop materials with superior performance to exhibit better capacity and output.

Korean Patent No. 10-1215829 (Patent Document 1) discloses a cathode active material such as LiCoO ₂ and LiNiO ₂ as an initial commercialized material, which has a disadvantage in that the crystal structure is unstable due to lithium desorption during charging. In addition, cobalt is known to be low in reserves, expensive, and toxic to humans. LiNiO ₂ having a layered structure as LiCoO ₂ will exhibit a high discharge capacity when charged to 4.0V or higher at a low cost as compared with LiCoO _2, can wake up the inflation phenomenon due to gas generation, or could be a thermal instability problems.

Lithium manganese oxide (LiMnO ₂ , LiMn ₂ O ₄ ) is a relatively abundant material and has attracted attention as a substitute for a cathode active material such as LiCoO ₂ or LiNiO ₂ mentioned above by using environmentally friendly manganese. Of these, LiMn ₂ O ₄ has the advantages of low unit cost and high output, but it has a disadvantage of low energy density. Therefore, research is underway to replace part of manganese with nickel. Japanese Patent Application Laid-Open No. 1996-171910 (Patent Document 2) discloses a method in which an alkali solution is mixed with an aqueous solution of Mn and Ni to coprecipitate Mn and Ni, followed by mixing lithium hydroxide and then firing to obtain LiNi _x Mn _1-x O ₂ 0.7 ≤ x ≤ 0.95). However, the thermal instability of nickel is still not solved and the capacity and life characteristics are not satisfactory. Therefore, there is a need for research and development of transition metal complex precursors capable of achieving superior performance.

Korean Patent No. 10-1215829 (2012.12.20.) Japanese Patent Laid-Open No. 1996-171910 (July 02, 1996)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a lithium secondary battery which is capable of eliminating thermal instability with high energy density and structurally high stability even when lithium ions are desorbed, And a cathode active material for a lithium secondary battery manufactured using the transition metal complex compound precursor.

The present invention also relates to a transition metal complex precursor which can reduce cost by containing manganese as a main component and can realize environment-friendly and more excellent performance, a process for producing the same, and a cathode active material for a lithium secondary battery The purpose is to provide.

According to an aspect of the present invention, there is provided a transition metal complex precursor comprising at least one selected from transition metal complex compounds represented by the following general formulas (1), (2) and (3)

[Chemical Formula 1]

Ni _x Mn _{1 -x} (OH) ₂

(In Formula 1, x is a real number satisfying 0 < x <

(2)

Ni _a Mn _b Co _{1 - (a + b)} (OH) ₂

(In the formula 2, a and b are real numbers satisfying 0 < a < 1, 0 < b <

(3)

Ni _a Mn _b Co _{1- (a + b + c)} M _c (OH) ₂

Wherein a, b and c are real numbers satisfying 0 < a <1, 0 < b < 1, 0 <c <1 and 0 <a + b + c < It is a trivalent metal element.)

In another aspect of the present invention, there is provided a method for preparing a precursor of a transition metal complex compound selected from the transition metal complex compounds represented by Chemical Formulas 1 to 3, comprising the steps of: preparing a metal aqueous solution by mixing a metal salt and distilled water; Adding an alkaline compound to the metal aqueous solution and mixing to prepare a mixture; And a step of adding a chelating agent to the mixture to precipitate the precursor.

Another aspect of the present invention relates to a cathode active material for a lithium secondary battery obtained from the above-mentioned transition metal complex compound precursor.

Another aspect of the present invention relates to a lithium secondary battery manufactured using the above cathode active material.

The cathode active material obtained from the transition metal complex compound precursor according to the present invention has advantages in cost reduction, cost competitiveness, environmental friendliness, high stability in lithium ion desorption and excellent in high temperature thermal stability.

Further, the present invention can provide a positive electrode active material for a lithium secondary battery that is excellent in charge / discharge capacity and life characteristics and can maximize battery efficiency.

1 to 3 are SEM photographs of transition metal complex precursor particles according to an embodiment of the present invention.
4 shows an X-ray diffraction pattern of LiMn ₂ O ₄ according to Comparative Example 2. Fig.
5 shows an X-ray diffraction pattern of the cathode active material according to Example 2 (A) and Example 3 (B) of the present invention.
6 is an XPS diagram showing Mn 2P of the cathode active material according to Example 2 of the present invention.
7 is an XPS diagram showing Mn 2P of a cathode active material according to Example 3 of the present invention.
8 is an XPS diagram showing Ni 2P of a cathode active material according to Example 2 of the present invention.
9 is an XPS diagram showing Ni 2P of a cathode active material according to Example 3 of the present invention.
10 is a graph showing a 50-cycle cycle charge / discharge evaluation (A: Example 8, B: Comparative Example 2) for confirming the life characteristics.

Hereinafter, the positive electrode active material for a lithium secondary battery obtained from the transition metal complex compound precursor of the present invention, the preparation method thereof, and the transition metal complex compound precursor will be described in detail. The present invention may be better understood by the following examples, which are for the purpose of illustration only and are not intended to limit the scope of protection defined by the appended claims. The technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs, unless otherwise defined.

The term &quot; transition metal complex compound precursor &quot; in the present invention includes any one precursor compound as well as any combination of two or more specific precursor compounds.

In the present invention, &quot; high density &quot; means that when the precursor is divided into the particle size (over 10 m), the neutral particle (5 ~ 10 m) and the small particle Precursor is mixed, meaning that the filling density of the precursor per the same volume is high.

Further, in the present invention, &quot; multimodal &quot; means a particle size distribution having two or more maximum points that are multimodality and clearly recognizable.

The present applicant has repeatedly carried out various experiments through long-term research. It has been found that when a precursor of a transition metal complex compound having manganese and having a specific composition is applied to a cathode active material of a lithium secondary battery, Discharge capacity and life characteristics can be remarkably improved. Thus, the present invention has been accomplished.

The transition metal complex compound precursor according to the present invention includes at least one selected from transition metal complex compounds represented by the following general formulas (1), (2) and (3)

[Chemical Formula 1]

Ni _x Mn _{1 -x} (OH) ₂

(In Formula 1, x is a real number satisfying 0 < x <

(2)

Ni _a Mn _b Co _{1 - (a + b)} (OH) ₂

(Wherein a and b are real numbers satisfying 0 < a < 1, 0 < b < 1 and 0 < a + b <

(3)

Ni _a Mn _b Co _{1- (a + b + c)} M _c (OH) ₂

Wherein a, b and c are real numbers satisfying 0 <a <1, 0 <b <1, 0 <c <1 and 0 <a + b + c < It is a trivalent metal element.)

In this case, the M in the formula (3) is not limited to a wide range within the range of achieving the object of the present invention. Preferably, the M is represented by Fe, Cu, Zn, Mg, Al, Cd, Ta, Ti, And the like. More preferably at least one selected from Fe, Mg, Al, Ti, Ta and Cr.

Each of the compounds represented by Chemical Formulas 1 to 3 is characterized in that the content of Mn is 20 to 80 mol%, preferably 30 to 70 mol% with respect to the total metal content. When the content of Mn satisfies the above range, not only high capacity and high output characteristics but also excellent structural stability and thermal stability can be realized and lifetime characteristics can be improved. Further, the content of Mn is preferably at least the content of Ni present in the compound, so that the above-mentioned effect can be further improved.

In each of the compounds represented by the general formulas (1) to (3), the content of Ni is preferably 35 mol% or less with respect to the total metal content in terms of thermal stability.

It is preferable that the content (mol%, P) of Mn and the content (mol%, Q) of Ni satisfy the following relational expression 1 in each of the transition metal complex compounds represented by the above general formulas (1) The following relational formula 1 shows the molar ratio relationship between the manganese and the nickel complex compound. The following relationship 1 is derived in consideration of the change of the performance of the battery depending on the content of manganese and the content of nickel.

(Relational expression 1) -0.2? {(P - S + 30) / P} - 1? 0.2

At this time, the above formula [{(P - S + 30) / P} - 1] preferably satisfies the range of -0.2 to 0.2, more preferably -0.15 to 0.15. When the above range is satisfied, high stability can be ensured when a combination of two or more components in the transition metal complex compound precursor is provided, and the lifetime characteristics and the capacity improving effect can be further increased.

In the present invention, the transition metal complex compound precursor may be any one selected from the compounds represented by Chemical Formulas 1 to 3, but may preferably have a combination of two or more components. More preferably, 1 to &lt; RTI ID = 0.0 &gt; 3, &lt; / RTI &gt;

When the transition metal complex compound precursor according to the present invention has two or more combinations of the compounds represented by the above general formulas (1) to (3), oxidation can be effectively prevented even when manganese is contained in an excess amount based on the entire transition metal, The spherical uniformity of the resulting precursor particles can be enhanced. In addition, the cathode active material obtained from the precursor can have a high density, which can dramatically improve the energy density and can further enhance the structural stability. Thus, it is possible to maximize the performance of the cathode active material, thereby improving the initial discharge capacity, It maximizes efficiency with lifetime characteristics and is able to realize excellent cycle characteristics over the long term.

The transition metal complex compound precursor according to an embodiment of the present invention is not limited to a particle size distribution within a range that achieves the object of the present invention, but a multi-modal particle size distribution is preferable in view of performance improvement. Preferably, it has a bimodal or trimodal particle size distribution. This is because the bimodal or tri-modal distribution in which the particle size distribution is a mixture of relatively large particles and small particles makes it possible to place small particles in an empty space between particles having a large size, This is because it is possible to realize a high bulk density and a discharge capacity as well as to improve the packing density when the cathode active material is manufactured.

At this time, the transition metal complex compound precursor has a multimodal particle size distribution and an average particle size of preferably 0.1 to 100 탆, more preferably 0.5 to 50 탆, can ensure a high density, and the reactivity with lithium It is good because it can improve the capacity per volume and is excellent in structural stability and can realize long-term stable performance.

FIGS. 1 to 3 are SEM photographs of the transition metal complex precursor particles according to an embodiment of the present invention, which have a multimodal particle size distribution in which alleles, neutral particles, and small particles coexist. This can realize a high density and have a high energy density.

The transition metal complex compound precursor according to an embodiment of the present invention may include Mn (OH) ₂ and at least one component selected from the transition metal complex compounds of the above formulas (1) to (3). That is, the transition metal complex compound precursor according to the present invention has a combination including a manganese-based hydroxide, thereby reducing the cost of using a single manganese-based compound and achieving high output performance. At the same time, in combination with any one or more components selected from the transition metal complex compounds of the above formulas (1) to (3), it is possible to exhibit a synergistic effect of realizing high density rather than a reduction in density due to the use of a single manganese compound.

The transition metal complex compound precursor according to an embodiment of the present invention may more preferably be a combination of two or more selected from the transition metal complex compounds represented by the general formulas (1), (2) and (3) have. This is because the physical properties of the respective precursors can be mutually compensated, and the synergistic effect can be realized in terms of thermal structural stability, battery capacity and lifetime characteristics to be achieved in the present invention.

In another aspect,

Mixing a metal salt and distilled water to prepare a metal aqueous solution;

Adding an alkaline compound to the metal aqueous solution and mixing to prepare a mixture; And

And a step of adding a chelating agent to the mixture to precipitate the precursor. The present invention also provides a method for producing a precursor of a transition metal complex compound selected from the following transition metal complex compounds represented by Chemical Formulas 1 to 3.

[Chemical Formula 1]

Ni _x Mn _{1 -x} (OH) ₂

(In Formula 1, x is a real number satisfying 0 < x <

(2)

Ni _a Mn _b Co _{1 - (a + b)} (OH) ₂

(Wherein a and b are real numbers satisfying 0 < a < 1, 0 < b < 1 and 0 < a + b <

(3)

Ni _a Mn _b Co _{1- (a + b + c)} M _c (OH) ₂

Wherein a, b and c are real numbers satisfying 0 <a <1, 0 <b <1, 0 <c <1 and 0 <a + b + c < It is a trivalent metal element.)

M in Formula 3 may include at least one selected from the group consisting of Fe, Cu, Zn, Mg, Al, Cd, Ta, Ti, V and Cr. And preferably at least one selected from Fe, Mg, Al, Ti, Ta and Cr.

The method for preparing the transition metal complex compound precursor of the present invention as described above can easily control composition, content, particle characteristics, concentration and reaction time of constituent elements, and can produce uniform particles, It is even better to achieve.

The transition metal complex compound precursor is prepared by a co-precipitation method, and can be prepared by simultaneously precipitating two or more transition metal elements using an precipitation reaction in an aqueous solution. In one embodiment, a transition metal complex compound containing two or more transition metals is mixed with a salt containing a transition metal in a predetermined molar ratio in consideration of the content of the transition metal to prepare an aqueous solution, and then an alkaline substance and a chelating agent To coprecipitate while keeping the pH alkaline, thereby preparing a transition metal complex precursor. At this time, precursor particle distribution, average particle size and the like can be easily controlled by controlling pH range, reaction temperature, reaction time, concentration of solution and the like. The coprecipitation reaction may be performed in multiple stages (seven stages or more), but is not limited thereto.

In the method for preparing a transition metal complex compound precursor according to an embodiment of the present invention, the pH of the mixture in the step of preparing the mixture may be 8 to 12, preferably 9 to 11. When the above-mentioned range is satisfied, the uniformity of the precursor particles can be enhanced and the precipitation can be performed well and the formation of particles is smooth, which is more preferable.

In the present invention, the alkaline compound is not particularly limited within the scope of attaining the object of the present invention, but is preferably selected from the group consisting of sodium hydroxide (NaOH), lithium hydroxide (LiOH) and potassium hydroxide (KOH) And may include one or more. It can adjust the pH, acts as a precipitant, and maintains a proper pH so that coprecipitation can occur smoothly.

In the present invention, the chelating agent may be one which is capable of supplying ammonium ions, but not limited to, ammonia water (NH ₄ OH), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), ammonium nitrate (NH ₄ NO ₃ ) and ammonium monophosphate ((NH ₄ ) ₂ HPO ₄ ). More preferably, the use of ammonia water is preferable because the shape of the precursor formed can be adjusted more uniformly. At this time, the weight ratio of the chelating agent to the metal aqueous solution is preferably 10: 1 to 1: 5, more preferably 8: 1 to 1: 3.

The metal aqueous solution is not particularly limited within the scope of attaining the object of the present invention, but it is preferable that the concentration of the metal aqueous solution is in the range of 1M to 3M, preferably 1M to 2M, more preferably 1.5M to 2.0M Range.

The temperature of the step of producing the metal aqueous solution is not particularly limited within the range of achieving the object of the present invention, but it is preferably 20 to 60 캜, preferably 30 to 50 캜, more preferably 35 to 45 캜 good.

Which is selected from the group consisting of the metal solution in the present invention containing a metal salt and has the anion of the metal salt is a sulfate (SO ₄ ^2-), nitrate (NO ₃ ^-), hydrochloride (Cl ^{- -)} and nitrate (COO) One or more may be used, but are not necessarily limited thereto. Preferably, the use of a sulfate is better in terms of productivity and physical properties of the resulting precursor.

A precipitate is obtained from the reaction, washed with pure water, and dried to obtain the desired transition metal complex compound precursor. In this case, drying is not particularly limited, but is preferably carried out at a temperature of 100 to 140 캜, more preferably 110 to 130 캜.

The present invention provides a cathode active material for a lithium secondary battery produced from a transition metal complex compound precursor as described above in another aspect.

The cathode active material for a lithium secondary battery can be obtained by preparing the lithium metal complex hydroxide by mixing the transition metal complex precursor and the lithium compound, and then firing the lithium metal complex hydroxide. In this case, a lithium compound, and is not intended to be used at least one selected from among lithium hydroxide (LiOH), lithium nitrate (LiNO _3), lithium carbonate (LiCO ₃₎ and lithium fluoride (LiF), limited. The weight ratio of the transition metal complex compound precursor and the lithium compound is 1: 0.9 to 1.5, preferably 1: 1 to 1.3. When the above range is satisfied, an excellent charge / discharge performance can be realized and the risk of gas generation at a high temperature can be prevented.

The cathode active material for a lithium secondary battery according to an embodiment of the present invention may have a bimodal or trimodal particle size distribution.

In addition, the cathode active material may have a multi-modal particle size distribution and preferably have an average particle size of 0.1 to 100 탆, more preferably 0.5 to 50 탆.

The step of calcining the lithium metal complex hydroxide may be performed by heat treatment at a temperature of 800 to 1,200 ° C, preferably 950 to 1,150 ° C. In this case, the heat treatment may be performed in the presence of oxygen, or may be performed in a mixed gas atmosphere or an air atmosphere in which oxygen and an inert gas are mixed. If the temperature is outside the above range, the bulk sintered body of agglomerates which are excessively agglomerated may be produced or the sintering may not be performed well.

The obtained cathode active material according to the present invention is obtained from the transition metal complex compound precursor as described above, and the particles may be uniform and homogeneously mixed. Further, the cathode active material may be spherical, which is better for improving the active material density of the cathode active material layer, for example, the tap density.

The cathode active material for a lithium secondary battery of the present invention may include at least one selected from the cathode active materials represented by the following formulas (4), (5) and (6).

[Chemical Formula 4]

LiNi _x Mn _{1 - x} O ₂

(In Formula 4, x is a real number satisfying 0 < x < 1).

[Chemical Formula 5]

LiNi _a Mn _b Co _{1 - (a + b)} O ₂

(Wherein a and b are real numbers satisfying 0 <a <1, 0 <b <1 and 0 <a + b <

[Chemical Formula 6]

LiNi _a Mn _b Co _{1- (a + b + c)} M _c O ₂

Wherein a, b and c are real numbers satisfying 0 <a <1, 0 <b <1, 0 <c <1 and 0 <a + b + c < It is a trivalent metal element.)

The cathode active material for the lithium secondary battery may further include LiMn ₂ O ₄ .

For example, when the cathode active material for a lithium secondary battery is LiMn ₂ O ₄ And the compound of formula 4, LiMn ₂ O ₄ And the compound of formula (4) is preferably 30 to 60:40 to 70. When the above numerical range is satisfied, high capacity and high output characteristics, excellent structural stability and thermal stability, and high lifetime characteristics can be exhibited.

When the positive electrode active material for a lithium secondary battery comprises LiMn ₂ O ₄ , the compound of Formula 4 and the compound of Formula 5, the weight ratio of LiMn ₂ O ₄ , the compound of Formula 4 and the compound of Formula 5 is 10:30 to 20:40: It is preferably 40 to 60. When the above numerical range is satisfied, high capacity and high output characteristics, excellent structural stability and thermal stability, and high lifetime characteristics can be exhibited.

When the positive electrode active material for a lithium secondary battery comprises LiMn ₂ O ₄ , the compound of the formula 4, the compound of the formula 5 and the compound of the formula 6, LiMn ₂ O ₄ , the compound of the formula 4, the compound of the formula 5, The weight ratio is preferably 10 to 30:10 to 30:20 to 40:20 to 40. When the above numerical range is satisfied, high capacity and high output characteristics, excellent structural stability and thermal stability, and high lifetime characteristics can be exhibited.

The present invention can manufacture an electrode or a secondary battery using the above-mentioned cathode active material. For example, the lithium secondary battery includes a cathode including a cathode active material, a cathode including a cathode active material, and an electrolyte existing between the cathode and the anode, and may optionally include a separator. At this time, the cathode active material of the present invention can be preferably used as the cathode active material.

One specific example of the lithium secondary battery in the present invention is as follows.

The positive electrode may be prepared by using the positive electrode active material according to the present invention, mixing a conductive agent, a binder and a solvent to prepare a positive electrode active material composition, and then directly coating and drying on the aluminum current collector. Or casting the positive electrode active material composition on a separate support, and then peeling the support from the support and laminating a film on the aluminum current collector.

The conductive agent may be at least one selected from carbon black, acetylene black, graphite, and metal powder. The binder may be at least one selected from the group consisting of vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, Polymethyl methacrylate, polytetrafluoroethylene, and mixtures thereof.

The solvent may be at least one selected from N-methylpyrrolidone, acetone, tetrahydrofuran and decane.

The content of the cathode active material, the conductive agent, the binder and the solvent is not particularly limited and can be used at a conventional level.

The negative electrode is prepared by mixing an anode active material, a binder and a solvent to prepare an anode active material composition. The anode active material composition is directly coated on the copper current collector or cast on a separate support, and the anode active material film peeled off from the support is laminated on the copper current collector can do. At this time, the negative electrode active material composition may further include a conductive agent.

As the negative electrode active material, a material capable of intercalating / deintercalating lithium is used. For example, lithium metal, a lithium alloy, coke, artificial graphite, natural graphite, an organic polymer combustible material, But is not limited thereto. The conductive agent, the binder and the solvent may be used in the same manner as the above-mentioned anode.

The lithium secondary battery may be a non-aqueous electrolyte or a known solid electrolyte as the electrolyte, and may be used without limitation as long as the lithium salt is dissolved.

The solvent of the non-aqueous electrolyte is not particularly limited, but cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and? -Butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides such as dimethylformamide, and the like can be used, and these can be used singly or in combination. Preferably, a mixed solvent of cyclic carbonate and chain carbonate is used. As the electrolyte, a gel polymer electrolyte in which an electrolyte is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N can be used. Wherein the lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCl, and LiI, but is not limited thereto. The separator is not particularly limited as long as it is commonly used in a lithium secondary battery. For example, polyethylene, polypropylene, polyvinylidene fluoride or a multilayer film of two or more thereof may be used.

The present invention provides a battery module including the lithium secondary battery as a unit cell, and a battery pack including the battery module. The battery pack is excellent in stability at a high temperature and can be used as a power source for a middle- or large-sized device requiring an excellent cycle characteristic and a high capacity for a long period of time because it has good initial charging / discharging capacity as well as life characteristics. Examples of the power source of the medium- and large-sized devices include an electric vehicle powered by an electric motor, an electric vehicle such as a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage system.

Hereinafter, the transition metal complex precursor according to the present invention and the cathode active material prepared using the same will be described. However, the present invention is not limited to the following examples.

(evaluation)

Charging and discharging  characteristic

(TOYO Corporation, TOYO-3100).

The electrical characteristics were evaluated by measuring charge / discharge capacities at 0.1C and 2.0C applied currents and 3.6 to 4.8V voltage ranges to measure discharge capacity and charge / discharge efficiency.

The coin cell prepared for evaluation was charged at a constant current (1.0 C) and a constant voltage (4.3 V, 110 mA cut-off) at 40 캜 for 10 minutes, rested for 24 hours, At a constant current (0.6 C) and a constant voltage (3.0 V, cut-off) discharge condition for 30 minutes. 50 cycles were performed under these conditions.

(Example 1)

In the case of preparing a transition metal complex compound precursor, it can be obtained by coprecipitation using a salt containing a transition metal and a basic substance. This coprecipitation method is a method of preparing a mixture of two or more kinds of transition metal salts at a desired molar ratio and controlling the reaction temperature, time, pH, concentration, etc. to control the diameter, distribution and density of the average particles.

Ni _{0 . In} order to prepare a complex compound precursor of _{3M 0 .7} (OH) ₂ , nickel sulfate and manganese sulfate were mixed in a molar ratio of 0.3: 0.7 by coprecipitation method, and a 1.7M metal aqueous solution was prepared. ), And nitrogen gas was injected at 2 L / min to remove dissolved oxygen. At this time, the temperature of the aqueous solution of the nitrogen contained in the reactor was maintained at 40 占 폚. NaOH solution was injected into the reactor to adjust the pH to 10.5 during the reaction. The total reaction time was 12 hours, and a powdery precursor precipitated at a period of 3 hours after the start of the reaction was obtained. The reaction was carried out by adding ammonia water again. After the reaction, the obtained transition metal precursor was washed with distilled water four times or more. The washed precursor was dried in a constant temperature drier at 120 ° C for 24 hours to synthesize a transition metal complex precursor Ni _0.3 Mn _0.7 (OH) ₂ .

(Example 2)

Ni _{0 . 25} Mn _{0 .} In the same manner as in Example 1 except that the transition metal solution are mixed in a molar ratio of _{0.4: 0.35: 35 Co 0 .4} (OH), nickel sulfate, manganese sulfate and cobalt sulfate 0.25 to manufacture ₂ Transition metal complex compound precursor Ni _{0 . 25} Mn _{0 . 35} was synthesized Co _{0 .4} (OH) _2.

(Example 3)

Ni _{0 . 3} Mn _{0 . 3} Co _{0 . 3} Mg to _{0 .1} (OH) to produce the _2, nickel sulfate, manganese sulfate, cobalt sulfate and magnesium sulfate 0.3 in the example except that the transition metal solution are mixed in a molar ratio of 0.1: 0.3: 0.3 1, the transition metal complex precursor Ni _{0 . 3} Mn _{0 . 3} Co _{0 . 3 0 .1} were synthesized Mg (OH) _2.

(Example 4)

Ni _{0 . 45} Mn _{0 .55} (OH) to produce the _second, the nickel sulfate and manganese sulfate 0.45: and a transition metal complex compound precursors in the same manner as in Example 1 except that the transition metal solution are mixed in a molar ratio of 0.55 Ni _0.45 Mn _0.55 (OH) ₂ was synthesized.

(Example 5)

Ni _{0 . 2} Mn _{0 .} For the production of _{25 Co 0 .55 (OH) 2} , nickel sulfate, manganese sulfate and cobalt sulfate 0.2 in the same manner as in Example 1 except that the transition metal solution are mixed in a molar ratio of 0.55: 0.25 Transition metal complex compound precursor Ni _{0 . 2} Mn _{0 . 25} was synthesized Co _{0 .55} (OH) _2.

(Example 6)

Ni _{0 . 15} Mn _{0 .85} (OH) to produce the _second, the nickel sulfate and manganese sulfate 0.15: and a transition metal complex compound precursors in the same manner as in Example 1 except that the transition metal solution are mixed in a molar ratio of 0.85 Ni _0.15 Mn _0.85 (OH) ₂ was synthesized.

(Example 7)

Ni _{0 . 45} Mn _{0 .} In the same manner as in Example 1 except that the transition metal solution are mixed in a molar ratio of _{0.4: 0.15: 15 Co 0 .4} (OH), nickel sulfate, manganese sulfate and cobalt sulfate 0.45 to manufacture ₂ Transition metal complex compound precursor Ni _{0 . 45} Mn _{0 . 15} was synthesized Co _{0 .4} (OH) _2.

(Comparative Example 1)

Mn (OH) ₂ was used as a precursor for comparison with the precursors according to the examples.

(Production of cathode active material)

The precursors according to Examples 1 to 7 and Comparative Example 1 were mixed with lithium carbonate (LiCO ₃ ) to prepare a lithium metal complex hydroxide. At this time, the cathode active material powder was prepared by heating at 1,000 ° C for 15 hours at a rate of 2 ° C / min with the weight ratio of the transition metal complex compound precursor and the lithium compound being 1: 1.3 (Table 1) .

(Preparation of Coin Cell)

Coin cells were prepared using the final cathode active materials prepared from Examples 1 to 7 and Comparative Example 1. The final cathode active material (weight fractions in parenthesis are shown) were classified into Examples 8 to 17 and Comparative Example 2. FIG. 4 is a graph showing the XRD of the cathode active material according to Comparative Example 2, and FIG. 5 is a graph showing the XRD of the cathode active material prepared from Example 2 (A) and Example 3 (B), respectively. 6 and 7 are XPS indicating Mn 2P of the cathode active material prepared in Examples 2 and 3, and FIGS. 8 and 9 are XPS indicating Ni 2P of the cathode active material prepared in Examples 2 and 3, respectively.

A mixture of 92 wt% of the final cathode active material prepared above, 2 wt% of carbon black as a conductive agent and 2 wt% of polyvinylidene fluoride (PVDF) as a binder in an amount of 4 wt% of N-methyl-2-pyrrolidone (NMP) The positive electrode slurry was coated on an aluminum (Al) thin film as a positive electrode current collector having a thickness of 20 mu m, vacuum dried, and roll pressed to prepare a positive electrode. And 1M LiPF ₆ EC: EMC (1: 2 vol%) was used as an electrolytic solution to prepare a coin cell type battery.

The coin cell produced in the above manner was classified into Examples 8 to 17 and Comparative Example 2 according to the final cathode active material applied, and the battery performance was evaluated and shown in Tables 2 and 3 below.

division Transition metal precursor Cathode active material Example 1 Ni _{0 . 3} Mn _{0 .7} (OH) ₂ LiNi _{0 . 3} Mn _{0 . 7} O ₂ Example 2 Ni _0.25 Mn _0.35 Co _0.4 (OH) ₂ LiNi _0.25 Mn _0.35 Co _0.4 O ₂ Example 3 Ni _0.3 Mn _0.3 Co _0.3 Mg _0.1 (OH) ₂ LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ Example 4 Ni _{0 . 45} Mn _{0 .55} (OH) ₂ LiNi _{0 . 45} Mn _{0 . 55} O ₂ Example 5 Ni _0.2 Mn _0.25 Co _0.55 (OH) ₂ LiNi _0.2 Mn _0.25 Co _0.55 O ₂ Example 6 Ni _{0 . 15} Mn _{0 .85} (OH) ₂ LiNi _{0 . 15} Mn _{0 . 85} O ₂ Example 7 Ni _0.45 Mn _0.15 Co _0.4 (OH) ₂ LiNi _0.45 Mn _0.15 Co _0.4 O ₂ Comparative Example 1 Mn (OH) ₂ LiMn ₂ O ₄

division Final cathode active material Initial battery capacity (mAh / g) Example 8 LiMn ₂ O ₄ (0.4) + LiNi _0.3 Mn _0.7 O ₂ (0.6) 147.2 Example 9 LiMn ₂ O ₄ (0.2) + LiNi _0.3 Mn _0.7 O ₂ (0.3) +
LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (0.5) 147.8 Example 10 LiMn ₂ O ₄ (0.2) + LiNi _0.3 Mn _0.7 O ₂ (0.2) +
LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (0.3) +
LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (0.3) 147.7 Example 11 LiMn ₂ O ₄ (0.2) + LiNi _0.15 Mn _0.85 O ₂ (0.2) +
LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (0.3) +
LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (0.3) 146.9 Example 12 LiMn ₂ O ₄ (0.2) + LiNi _0.3 Mn _0.7 O ₂ (0.2) +
LiNi _0.45 Mn _0.15 Co _0.4 O ₂ (0.3) +
LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (0.3) 147.1 Example 13 LiMn ₂ O ₄ (0.2) + LiNi _0.3 Mn _0.7 O ₂ (0.2) +
LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (0.1) +
LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (0.5) 146.8 Example 14 LiMn ₂ O ₄ (0.2) + LiNi _0.3 Mn _0.7 O ₂ (0.2) +
LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (0.5) +
LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (0.1) 147.2 Example 15 LiNi _{0 . 3} Mn _{0 . 7} O ₂ (1.0) 146.6 Example 16 LiNi _0.25 Mn _0.35 Co _0.4 O ₂ (1.0) 146.3 Example 17 LiNi _0.3 Mn _0.3 Co _0.3 Mg _0.1 O ₂ (1.0) 146.7 Comparative Example 2 LiMn ₂ O ₄ (1.0) 146.9

division Lithium secondary battery life characteristics
(50 times / discharge capacity (%)) Output Characteristics
(0.1C / 2.0C) (%) Example 8 88.6 96.8 Example 9 88.9 97.0 Example 10 90.2 98.6 Example 11 87.9 95.5 Example 12 87.6 95.1 Example 13 87.1 94.9 Example 14 87.3 95.1 Example 15 86.9 95.2 Example 16 87.3 95.8 Example 17 87.5 95.4 Comparative Example 2 85.1 92.3

As shown in the above table, in the case of the lithium secondary battery including the cathode active material obtained using the transition metal complex precursor produced according to the present invention (Examples 8 to 17), the battery prepared only with the manganese hydroxide precursor The battery capacity, the charge / discharge capacity, the efficiency and the life span characteristics were superior to those of Comparative Example 2).

FIG. 10 is a graph showing a 50-cycle cycle charge / discharge evaluation. The long-life characteristics of Example 10 (A) were superior to those of Comparative Example 2 (B).

In Examples 15 to 17, the cathode active material was prepared as a single precursor instead of the combination of the transition metal complex precursors according to the present invention. As shown in Examples 8 to 10, the combination of the transition metal complex precursors It was confirmed that the physical properties were somewhat deteriorated in the initial cell capacity and lifetime characteristics as compared with the use of the prepared cathode active material.

Claims (10)

delete delete delete delete delete delete LiMn ₂ O ₄ ;
A compound of formula (4);
A compound of formula 5; And
A cathode active material for a lithium secondary battery comprising a compound represented by the following formula (6)
The positive electrode active material has an average particle diameter of 0.1 to 100 탆,
Wherein the weight ratio of LiMn ₂ O ₄ , the compound represented by the following general formula (4), the compound represented by the general formula (5) and the compound represented by the general formula (6) is 10-30: 10-30: 20-40: 20-40.
[Chemical Formula 4]
LiNi _x Mn _1-x O ₂
(In Formula 4, x is a real number satisfying 0 < x < 1).
[Chemical Formula 5]
LiNi _a Mn _b Co _{1- (a + b)} O ₂
(Wherein a and b are real numbers satisfying 0 <a <1, 0 <b <1 and 0 <a + b <
[Chemical Formula 6]
LiNi _a Mn _b Co _{1- (a + b + c)} M _c O ₂
Wherein a, b and c are real numbers satisfying 0 <a <1, 0 <b <1, 0 <c <1 and 0 <a + b + c < It is a trivalent metal element.)
8. The method of claim 7,
Wherein M in Formula 6 is selected from the group consisting of Fe, Cu, Zn, Mg, Al, Cd, Ta, Ti, V and Cr.
delete A lithium secondary battery comprising the cathode active material of claim 7.

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