WO2013125798A1

WO2013125798A1 - Method for manufacturing cathode active material for lithium secondary battery

Info

Publication number: WO2013125798A1
Application number: PCT/KR2013/000715
Authority: WO
Inventors: 정연욱; 김원태; 강경완
Original assignee: 경북대학교 산학협력단
Priority date: 2012-02-20
Filing date: 2013-01-29
Publication date: 2013-08-29
Also published as: KR101418060B1; KR20130095572A

Abstract

The present invention relates to a method for manufacturing a cathode active material for a lithium secondary battery and, more particularly, to a method for manufacturing a cathode active material for a lithium secondary battery, comprising: generating manganese complex deposit by restoring and depositing manganese and heterogeneous metal elements from a mixed solution containing a manganese compound and a heterogeneous metal element compound; and generating lithium manganese complex oxide by mixing the manganese complex deposit with a lithium-contained metal compound and firing the mixture at 400 to 750 ºC. According to the present invention, a cathode active material for a lithium secondary battery in which vanadium is effectively doped into lithium manganese complex oxide can be manufactured, and the use thereof enables the production of a lithium secondary battery having improved capacity and remarkably improved charging and discharging efficiency.

Description

【Specification】

[Name of invention]

Manufacturing method of positive electrode active material for lithium secondary battery

[Technical Field]

The present invention provides a method for preparing excellent capacity characteristics and relates to a manufacturing method of the charge-discharge efficiency is possible ⁱ cathode active material for a lithium secondary battery, and more particularly, manganese and vanadium or niobium, such as by reducing precipitation with a cathode active material for a lithium secondary battery It is about.

Background Art

Lithium secondary batteries, which are currently in commercial use, have a mean discharge potential of 3.7 V, or 4 V, which is the heart of the digital age that is rapidly being applied to portable phones, notebook computers, camcorders, etc., which are referred to as 3C.

As a cathode active material of such a lithium secondary battery, a composite oxide such as LiCo0 ₂ , LiMn ₂ 0 ₄ , LiNi0 ₂ , LiNii Co _x 0 _2> LiMn0 _2, or the like is used. LiCo0 ₂ exhibits good electrical conductivity, high battery voltage, and excellent electrode characteristics, and is a representative cathode active material currently commercialized and sold by SONY, etc., but has a disadvantage of being expensive. LiNi0 ₂ is the least expensive of the above-mentioned cathode active materials, and exhibits the highest discharge capacity of the battery, but has a disadvantage in that it is difficult to synthesize.

More than 95% of the batteries currently in circulation around the world

LiCo¾ is used and a lot of efforts are being made to replace LiCo0 ₂ . Accordingly, studies on Mn-based cathode active materials such as LiMn ₂ O ₄ , LiMn0 ₂ , which are easy to synthesize, relatively inexpensive, and which have little pollution to the environment, are actively conducted. However, LiMn ₂ O ₄ and LiMnO ₂ have a problem in that the capacity is small and the layer discharge efficiency is poor depending on repeated use.

Therefore, there is a need for research on development of a cathode active material and process for lithium secondary batteries that have improved capacity when used in lithium secondary batteries, excellent layer discharge efficiency, and reduced production cost compared to LiCo0 ₂ .

[Content of invention]

[Problem to solve] The present invention is to provide a method for producing a positive electrode active material for a lithium secondary battery containing a lithium manganese-based composite ^" oxide having improved capacity and excellent layer discharge efficiency through a reduced precipitation method such as manganese and vanadium or niobium. To provide a cathode active material for a lithium secondary battery prepared by the above method.

The present invention also provides a lithium secondary battery including the cathode active material.

[Measures of problem]

The present invention comprises the steps of producing a manganese complex precipitate by reducing precipitation of manganese and dissimilar metal elements from a mixed solution comprising a manganese compound and a dissimilar metal compound including at least one dissimilar metal element selected from the group consisting of V and Nb; It provides a method for producing a positive electrode active material for a lithium secondary battery comprising a; and mixing the manganese composite precipitate and the lithium compound, and calcining under conditions of 300 to 800 ^° C to produce a lithium manganese composite oxide represented by the following formula (1) .

[Formula 1]

Lii + a Mni-bMb) ^

In the formula, a is 0 <a <l / 3, b is 0 <b <0.5, and M is at least one metal element selected from the group consisting of V and Nb.

The present invention also provides a cathode active material for a lithium secondary battery produced by the above method.

The present invention also provides a lithium secondary battery comprising the cathode active material.

Hereinafter, a method of manufacturing a cathode active material for a lithium secondary battery according to a specific embodiment of the present invention, a cathode active material for a lithium secondary battery manufactured according to this, and a lithium secondary battery including the same will be described in detail. However, this is presented as an example of the invention, whereby the scope of the invention is not limited, it is apparent to those skilled in the art that various modifications to the embodiments are possible within the scope of the invention.

Unless otherwise stated throughout this specification, "including" or "containing" The term "comprising" includes any component (or component) without limitation and should not be construed to exclude the addition of other components (or components).

In the present invention, "lithium secondary battery" refers to one that can continuously perform layer charge and discharge. This lithium secondary battery has a feature of a medium for storing electrical energy. However, as described above, the lithium secondary battery (a cathode active material for a lithium secondary battery) should have structural stability because it must escape in the form of silver upon desorption, and is manufactured in a part where a transition metal material having such structural stability should be mainly used. There are limited disadvantages of the process and materials.

Accordingly, the present invention provides a cathode active material by reducing and precipitating manganese and vanadium, thereby improving capacity when used in a lithium secondary battery, excellent layer discharge efficiency, and excellent in low-temperature firing process in which production cost is reduced compared to LiCo0 ₂ . Process improvement effect can be obtained.

In particular, the experimental results of the present inventors, it was found that by producing a positive electrode active material by the method of reduction precipitation and doping and applied to a lithium secondary battery, it is possible to secure excellent characteristics that can maintain a constant discharge capacity. In general, Li ₂ Mn0 ₃ active material is rich in Li can realize a large capacity when used alone, Mn is due to the Mn elution generated in LiMn ₂ 0 ₄ because Mn takes the most stable form of tetravalent in the active material There is no stability problem. In addition, most spinel or layered positive electrode active materials undergo a volume change when lithium is repeatedly inserted and ^' desorbed, thereby causing some structures to collapse, causing capacity reduction. However, since Mn 4 is the most stable form, structural collapse does not occur easily. In addition, current cathode active material suitable for HEV or EV requires a high output, Mn 4 must be driven at 4.4V or higher in order to be activated, and when activated is possible to use a high voltage of 4.8 ~ 5V.

A disadvantage of the known cathode active material is that the first discharge capacity is large, but the capacity tends to decrease as the cycle progresses. This lasted This is because Li ₂ O is generated during the cycle, which causes the oxygen in the structure to continue to be lost, thereby preventing Mn from maintaining tetravalent. Accordingly, in the present invention, Mn is a mixed valency having an oxidation number between tetravalent and trivalent and tetravalent through doping with a heterovalent hetero element such as vanadium or niobium, thereby enabling activation even at 4.4 V or less. It is possible to increase or maintain the capacity by improving the collapse of the structure. At present, the positive electrode active material of the present invention has a half composition of Li ₂ Mn¾ when preparing Ni [Ni _x Co _y Mn _z ] 0 ₂ having a Ni-rich composition, thereby providing initial charge / discharge. In order to use Li ₂ Mn0 ₃ lithium at the time of capacity expression, production and electrochemical properties are measured and are in a funny situation.

Accordingly, according to one embodiment of the present invention, there is provided a method of manufacturing a cathode active material for a lithium secondary battery in which the manganese, vanadium (V), niobium (Nb), and the like are reduced and precipitated together by optimizing the process conditions of a predetermined step.

In the method of manufacturing a cathode active material for a lithium secondary battery, manganese and dissimilar metal elements are reduced-precipitated by using a mixed solution containing a heterometal compound and a manganese compound containing at least one heterometal element selected from the group consisting of V and Nb. Producing a manganese composite precipitate; And mixing the manganese composite precipitate and the lithium compound, followed by baking under conditions of 300 to 800 ^° C. to produce a lithium manganese composite oxide represented by the following Formula 1.

[Formula 1]

Lii + aCMni-bMb)! ^

Wherein a may be 0 <a <l / 3; b may be 0 <b <0.5, preferably 0 <b <0.3, more preferably 0 <b <0.2; M may be one or more metal elements selected from the group consisting of V and Nb.

In particular, in the formula (1), the indexes of a and b are 0 ≦ a ≦ l / 3, 0 <b <0.5, preferably 0 ≦ a ≦ l / 3, in the case of vanadium (V) doped lithium manganese composite oxide. 0 <b <0.3 ₍ more preferably 0 <a <l / 3, 0 <b <0.2), and in the case of a niobium (Nb) doped lithium manganese composite oxide, 0 ≦ a ≦ l / 3, 0 <b <0.3, preferably 0 ≦ a ≦ l / 3, 0 <b <0.25, more preferably 0 <a <l / 3 ₍ can be 0 <b <0.2)

The lithium manganese composite oxide may be represented by the following formula (2).

[Formula 2]

_{_{Li 4/3 (Mni- x M}} x) 2 302

Wherein X is 0 ≦ x ≦ 0.5, preferably 0 ≦ x ≦ 0.3, more preferably

0 ≦ x ≦ 0.2; M is at least one metal element selected from the group consisting of V and Nb.

In the lithium manganese composite oxide is _{_{_{Li 4/3 (Mn 0. 95 V}}} 0. 05) 2/3 0 2, L i 4/3 (Mn 0. 9 Vo. L) 2 / 3O2, L i 4/3 _{(Mn 0 .85V0.15) 2 / 3O2} , L i 4/3 (Mn 0. 95 Nbo .05) 2 / 3O2, Li 4 /3(Mno.9Nbo.i)2/302, Li 4/3 ( _{_{_{_{Mn 0. 995 Nb 0. 05}}}} ) can be given alone or in combination of two or more, such as ₀₂ _2/3. .

In the present invention, the manganese composite precipitate which is a precursor of the lithium manganese composite oxide is produced by reduction precipitation of manganese (Mn), vanadium (V), niobium (Nb), etc., and vanadium together with manganese (Mn). It includes one or more metal elements selected from the group consisting of (V) and niobium (Nb) simultaneously. The manganese composite precipitate of the present invention is characterized by exhibiting an amorphous phase. In addition, due to the high enthalpy energy of these amorphous crystalline phases, it is also possible to use a heat treatment process (500-600 ^° C.) which is significantly lower than a solid process (solid-state react ion) involving a heat treatment process at a high temperature of 800 V or higher. It is possible to obtain a single crystal phase such as the final Li ₂ Mn0 _3, and because the heat treatment temperature is low, the particle size can also be controlled as desired.

In particular, in the conventional wet process, the precursor of the lithium composite oxide is formed in the crystal phase form of hydroxide (NiCoMn-ΟΗ) or an oxide compound by coprecipitation method. There is a problem that needs to be done. However, in the case of the present invention, it is possible to produce an amorphous lithium manganese composite oxide precursor, the final lithium manganese composite oxide in the form of a single crystalline crystal of excellent crystallinity even if the firing process at a significantly lower temperature, such as conventional wet process There is an advantage to get it. In the present invention, the step of reducing precipitation of manganese (Mn) and vanadium (V) or niobium (Nb) to produce a manganese complex precipitate is pH 9 to 13, preferably pH 9.5 to 12.5, more preferably pH 10 to It can carry out under the conditions of 12. The pH range is a value corresponding to a mixed solution in which both dissimilar metal compounds and manganese compounds containing sub-metallic elements such as vanadium (V) and niobium (Nb) are dissolved. In order to reduce and precipitate heterogeneous metal elements such as vanadium (V) and niobium (Nb) together with manganese (Mn) in the mixed solution, the pH value may be 9 or more, and the pH value in terms of precipitation and composition change This can be 13 or less.

The pH value may be adjusted using a reducing agent in the mixed solution, and as the reducing agent, one or two or more selected from the group consisting of KBH ₄ , LiBH ₄ , NaBH ₄ , NaAlH ₄ , and LiAl¾ may be used. The reducing agent is preferably NaBH ₄ , KBH ₄ and the like in terms of preparing the precipitate in the amorphous form. In addition, by adding an acid or a basic compound in addition to the reducing agent may be used to adjust the pH value to the optimum range or to prevent the sudden rise of the pH value. Such acidic compounds include HCl, HC10 ₄ , H ₂ S0 ₄ , HBr, and the like, and basic compounds include ammonia, KOH, LiOH, NaOH, NH ₄ 0H, CH ₃ COOH, and HCN. However, when the basic compound is added alone without the reducing agent as described above, manganese (Mn), vanadium (V), niobium (Nb), and the like may not be precipitated at the same time, for example, only Mn ₃ 0 ₄ may precipitate, which may be undesirable. have.

On the other hand, the mixed solution containing both a manganese compound and a metal compound containing a dissimilar metal element such as vanadium, niobium, etc. First, the dissimilar metal compound is pH 13 to 13, preferably pH 10 to 12, more preferably pH After dissolving in the basic solvent of 10-11, it can manufacture by dissolving a manganese compound here. However, the manganese compound may be added after adjusting the manganese compound to pH 2-6, preferably pH 3-5, more preferably pH 4-5 of the solution containing the dissimilar metal compound according to the pH range. Can be.

Here, as the manganese compound, manganese sulfate, manganese nitrate, manganese acetate, Manganese Acet Manganese chloride, manganese dioxide, manganese trioxide, and one or more selected from the group consisting of manganese tetraoxide can be used. Among them, it is more preferable to use manganese sulfate, manganese nitrate, or manganese acetate in terms of dissolution of manganese raw materials. In addition, the vanadium compound, vanadium metal, vanadium oxide (V ₂ 0 ₅ , V ₂ O ₄₎ V ₂ 0 ₃ , V ₃ O ₄₎ , vanadium oxychloride, vanadium tetrachloride, vanadium trichloride, ammonium metavanadate, metavanadium acid At least one selected from the group consisting of sodium and potassium metavanadate, lithium chloride, niobium oxide (Nb Nb0 ₂ , Nb ₂ 0 ₅ ), niobium chloride, and niobium phosphide may be used. Among them, it is more preferable to use vanadium oxide, sodium metavanadate, niobium oxide, or the like in terms of dissolution of the dissimilar metal element raw material.

In addition, the molar ratio of the dissimilar metal elements such as vanadium and niobium to manganese may be 0.01 to 0.50 mol, preferably 0.02 to 0.20 mol, more preferably 0.05 to 0.15 η) 1. The molar ratio of the vanadium to manganese in terms of the minimum substitution amount of the dissimilar metal elements may be 0.01 mol or more, and the molar ratio of the vanadium to manganese in the maximum substitution amount of the dissimilar metal elements may be 0.50 mol or less.

The present invention may further include the step of drying the lithium manganese composite oxide precursor generated from the reduction precipitation step. The drying step may be carried out under 40 to 150 ^° C, preferably 80 to 130 ^° C, more preferably 100 to 120 ^° C conditions.

On the other hand, the manganese composite precipitate obtained after drying is mixed with a lithium compound, lithium manganese through a heat treatment step of firing under conditions of 300 to 800 V, preferably 350 to 700 ^° C, more preferably 400 to 620 ^° C Can be converted to complex oxides. This firing process may be performed by a two-step heat treatment process including a first heat treatment and a second heat treatment. Here, the first heat treatment for 7 to 15 hours at a temperature of 300 to 700 ^° C, preferably for 9 to 14 hours at a temperature of 350 to 600 ^° C, more preferably at a temperature of 400 to 550 ^° C It may be carried out by heating for 10 to 13 hours. In addition, the secondary heat treatment for 10 to 20 hours at a temperature of 300 to 800 ^° C after the first heat treatment, preferably 400 to It may be carried out by heating for 14 to 18 hours at a temperature of 700 ^° C. more preferably for 15 to 17 hours at a temperature of 440 to 620 ^° C.

In the present invention, the lithium compound may be at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium sulfite, lithium fluoride, lithium nitrate, lithium bromide, lithium oxide and lithium chloride. Preferably, lithium hydroxide, lithium carbonate, etc. can be used.

The molar ratio of lithium to manganese may be reacted to be 1.60 to 1.80 mol, preferably 1.65 to 1.78 mol, more preferably 1/70 to 1.75 mol. In terms of single phase production, the molar ratio of lithium to manganese may be 1.60 mol or more, and the molar ratio of lithium to manganese may be 1.80 mol or less in terms of controlling the intensity ratio of each surface index. have.

On the other hand, according to another embodiment of the present invention, there is provided a cathode active material for a lithium secondary battery manufactured by the method as described above. The cathode active material for a lithium secondary battery may include a lithium manganese composite oxide represented by Formula 1 below.

[Formula 1]

Lii _{+ a} (Mni-Mb) i-a02

Wherein a may be 0 <a <l / 3; b may be 0 <b <0.5, preferably 0 <b <0.3, more preferably 0 ≦ b ≦ 0.2; M may be one or more metal elements selected from the group consisting of X and Nb.

In particular, in the formula (1), the index of a, b is vanadium (V) doped lithium manganese composite oxide ^■ 0 ≦ a ≦ l / 3, 0 <b <0.5, preferably 0 <a ≦ l / 3 , 0 <b <0.3, more preferably 0 <a <l / 3, 0 <b <0.2, and 0 ≦ a ≦ l / 3 for niobium (Nb) doped lithium manganese composite oxide , 0 <b <0.3, preferably 0 ≦ a ≦ l / 3, 0 <b <0.25, more preferably 0 <a <l / 3, 0 <b <0.2.

The lithium manganese composite oxide may be represented by the following formula (2). [Formula 2]

_{_{_{Li 4 3 (Mni- x M x}}} ) 2/302 Wherein x may be 0 ≦ x ≦ 0.5, preferably 0 ≦ x ≦ 0..3, more preferably 0 ≦ χ ≦ 0.2; Μ is at least one metal element selected from the group consisting of V and Nb.

The lithium manganese composite oxide as the _{_{_{Li 4/3 (Mn 0. 95 V}}} 0. 05) 2/3 0 2, Li4 / 3 (Mno.gV 0 .1) 2/302, L i 4/3 (Mno. ssVo.15) 2/302, L i 4/3 (Mno. ₉₅ Nbo .05) 2 / 3O2,

Li ₄ /3(Mno.9Nbo.i) there may be mentioned _{_{2/302, Li 4/3 (Mn}} 0. 995 Nb 0. 05) 1 alone or in combination of two or more, such as ₀₂ _2/3. . The positive electrode active material for a lithium secondary battery manufactured according to the present invention has a discharge capacity of 140 mAhg ^{"" 1} or more at two or more cycles measured according to the method evaluated by using a case of SUS product as a test cell for electrode evaluation. 140 to 220 mAhg ^"1, preferably from 170 to 210 ^{mAhg" 1,} more preferably 180 to 200 mAhg ^_1 7> may be.

On the other hand, according to another embodiment of the present invention, there is provided a lithium secondary battery comprising the positive electrode active material for the lithium secondary battery. The lithium secondary battery is characterized by improving the electrochemical properties of the existing material by using a cathode active material prepared by reducing precipitation of manganese and vanadium to produce a single-phase lithium manganese composite oxide. .

In particular, the lithium secondary battery of the present invention includes a cathode including a cathode active material; An anode including an anode active material; And a separator between the anode and the cathode.

The lithium secondary battery of the present invention may include various negative electrode active materials having a wide range of characteristics.

In the present invention, matters other than those described above can be added or subtracted as necessary, and therefore the present invention is not particularly limited.

【Effects of the Invention】

According to the present invention, by reducing and precipitating together manganese, vanadium, niobium, etc., a capacity can be improved, and a cathode active material for a lithium secondary battery of LiMnO ₂ system having excellent layer discharge efficiency can be manufactured.

In addition, production of a cathode active material for a lithium secondary battery according to the present invention reduces production costs, improves capacity, and has excellent charge and discharge efficiency. There is an effect to manufacture a secondary battery.

[Brief Description of Drawings]

1 is a photograph showing the SEM measurement results for the precursor (precursor), that is, manganese composite precipitate obtained by co-reduction of manganese and vanadium according to Example 1 of the present invention.

2 is a precursor obtained by co-reduction of manganese and vanadium according to Example 1 of the present invention, namely; It is a graph showing the XRD measurement result (intensity in 2theta degree: intensity, a.u.) for manganese composite precipitate.

Figure 3 is a graph showing the V doped ryangbyeol XRD measurement results with respect to the lithium-manganese composite oxide prepared by the reduction precipitation method according to the embodiment 1-6 of the present invention Example _{_{1:. Li 4/3 (Mn 0}} 95 V ₀ ₀₅₎ _2/3 0 ₂ example _{2:. Li 4/3 (} Mno.9Vo 1) 2/30 2, example _{3:.. Li 4/3 (Mn} 0.85 V 0 15) 2/3 0 ₂ example _{_{_{4: Li 4/3 (Mn 0 95}}} Nb 0 05..) 2/3 0 2, example _{_{5: Li 4/3 (. Mn 0}} 9 Nbo.i) 2/30 2, example _{_{6: Li 4/3 (Mno}} 85 Nbo.i5.) 2 / 3C) 2, the control _{_{_{group: Li 4/3 Mn2 / 3}}} 02]. 4 is a lithium manganese composite prepared by the reduction precipitation method according to Examples 1 to 3 of the present invention. It is a photograph which shows the SEM measurement result by V doping amount with respect to an oxide (Example 1: M = V, b <0.05, Example 2: M = V, b <0.10, Example 3: M = V b <0.15).

5 is a graph showing the XRD measurement results by V doping amount for the lithium manganese composite oxide prepared by the dry method according to Comparative Examples 1 to 6 of the present invention [Comparative Example 1: Li _4/3 (Mno. ₉₅ V _0. ₀₅ ) _2/3 0 _2, Comparative example _{_{2: Li 4 /3(Mno.9Vo.i) 2/}} 302) Comparative example _{_{3:. Li 4/3 (Mn 0}} 95 Nb 0.05) 2/3 0 2, Comparative example _{_{4: Li 4/3 (Mn}} 0 9 Nb 0..) 2/302, Comparative example _{_{5: Li 4/3 (Mno 85 Vo.i}} 5.) 2/30 2, Comparative example 6: Li _{_4/3} ( _{_{_{_{. Mno.85Nb 0 15) 2/3}}}} 0 2, the control _{_{_{group: Li 4/3 Mn 2/}}} 3 0 2]. Figure 6 is a photograph showing the SEM measurement results by V doping amount for the lithium manganese composite oxide prepared by the dry method according to Comparative Examples 1 to 4 of the present invention (Comparative Example 1: M = V, b <0.05, Comparative Example 2: M = V, b <0.10, Comparative Example 3: M = Nb, b <0.05, Comparative Example 4: M = Nb, b <0.10).

7 is a graph showing the results of measuring the electrochemical characteristics of the lithium manganese composite oxide prepared by the reduction precipitation method according to Examples 1 to 3 of the present invention [Example 1: M = V, b≤0.05 (wet), Example 2: M = V, b ≦ 0.10 (wet), Example 3: M = V, b≤0.15 (wet)].

8 is a graph showing the results of measuring the electrochemical characteristics of the lithium manganese composite oxide prepared by the dry method according to Comparative Examples 1 to 4 of the present invention [Comparative Example 1: M = V, b <0.05 (dry), Comparative Example 2: M = V, b≤0.10 (dry), Comparative Example 3: M = Nb, b <0.05 (dry), Comparative Example 4: M = Nb, b <0.10 (dry)].

9 is a graph showing the life characteristics measurement results for the lithium manganese composite oxide prepared by the reduction precipitation method according to Examples 1 to 3 of the present invention and the lithium manganese composite oxide prepared by the dry method according to Comparative Example 1-4 [ discharge capacity per cycle, example _{_{_{1: Li 4/3 (Mn 0 95}}} V 0 05..) 2/3 0 2 Wet process, example _{2: Li 4/3 (Mn} 0 .9Vo.i) 2/30 Wet process _2, example _{_{3: Li 4 /3(Mno.85Vo.i5)2/30 2 Wet process}} , Comparative example _{_{1: Li 4/3 (.}} . Mn 0 95 V 0 05) 2/30 2 302 Solid process, Comparative example _{_{2: Li 4/3 (Mn}} 0 9 V 0 .i.) 2/302 Solid process, Comparative example 3: L i 4/3 (. Mn 0 gsNbo .05) 2/302 Solid process, comparison 14: Li 4/3 (Mno.gNbo. ₁₎ 2/302 Sol id process].

10 is a U / M ratio (ratio) with respect to the present embodiment the lithium-manganese composite oxide prepared by the reduction precipitation method according to the example 3 of the invention _{_{(Li 4/3 (Mno. 85 V}} 0. 15) 2/3 0 2) A graph showing the results of XRD measurement of single phase formation.

11 is a SEM measurement results measured after further heat treatment at a high temperature for the lithium manganese composite oxide prepared by the reduction precipitation method according to Example 2 of the present invention and the lithium manganese composite oxide prepared by the dry method according to Comparative Example 2 (A) Example 2, (B) Comparative Example 2L

12 is an XRD measurement measured after heat treatment at a high temperature for a lithium manganese composite oxide prepared by the reduction precipitation method according to Examples 2 and 3 of the present invention and a lithium manganese composite oxide prepared by the dry method according to Comparative Example 2. the result is a graph showing [example _{2: Li 4/3 (Mno} 9 Vo.i.) 2/302 Wet process, example _{_{3: Li 4/3 (.}} . Mn 0 85 V 0 15) 2/3 0 ₂ Wet process, Comparative Example 2: Li 4/3 (Mno. ₉ Vo.i) 2/30 ₂ Solid process].

[Specific contents to carry out invention]

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples. Example 1

After dissolving 3.05 g of LiOH and 2.84 g of KOH in .500 mL of distilled water to prepare a basic solvent having a pH of 10.5, a vanadium compound (V ₂ 0 ₅ , 98%) was dissolved in the basic solvent. The basic solution in which V ₂ 0 ₅ was dissolved was lowered to pH 4 by using dilute HC1, and then dissolved in manganese compounds (MnS0 ₄ · 5¾0, 98%) to obtain a transparent light brown solution without a separate precipitate.

In this manner, a reducing agent (KBH ₄ ) solvent was added to a solution in which both the vanadium compound and the manganese compound were dissolved, and then raised to pH 10-12, thereby obtaining a complex compound in which vanadium and manganese were precipitated together as a dark brown precipitate. At this time, HC1 was used to suppress a sharp increase in pH, and ammonia water was used to raise the desired pH to 11.5 because pH 9 was the limit of the reducing agent alone. The vanadium manganese composite precipitate thus produced was washed with water to remove impurities, and then dried at 80 ^° C. for at least 8 hours. The obtained semi-manganese composite precipitate was completely amorphous by XRD analysis (see FIG. 2).

The dried vanadium manganese composite precipitate was mixed with a lithium compound (Li ₂ CO ₃ , 98%) and a molar ratio (Li / Mn ratio) of 1. group. Thereafter, a uniform mixture was obtained by planetary ball milling using a 10 mm ball.

The lithium manganese vanadium composite mixture powder was put into a tube furnace, and the temperature was raised at a rate of 3 ^° C. per minute to raise the temperature to 400-550 ^° C. (Celsius), followed by oxygen gas for 12 hours. The primary heat treatment was performed while maintaining while adding. Thereafter, the temperature was raised at a rate of 3 ^° C. per minute to further increase the temperature of about 40 to 70 ^° C compared to the first heat treatment, that is, to raise the temperature to 440 ~ 620 ° C, and then in this state for 16 hours The secondary heat treatment was performed while maintaining while adding oxygen gas. Dark red color of the lithium-manganese composite oxide according to the present invention by carrying out the process to produce a Formula _{_{_{Li 4/3 (Mn 0.95 V 0.}}} 05) 2/3 0 2] was prepared in the cathode active material for a lithium secondary battery.

The powder obtained by the heat treatment was examined for particle size and structure using SEM and XRD. As a result of analysis, the synthesized powder was uniform in particle size and phase. A single crystalline phase was shown.

Example 2

Example 1, except that the amorphous reducing precipitate was prepared by varying the content of the vanadium compound (V ₂ 0 ₅ ) and the manganese compound (MnS0 ₄ ᅳ 5¾0) such that the molar ratio of the metal component was Mn: V = 0.9: 0.1. In the same manner as in the lithium secondary battery cathode active material [Li _4/3 (Mno. GVo. ^ / Sod) was prepared and the particle size and structure was confirmed by using the SEM, XRD in the same manner.

Example 3

Example 1, except that the amorphous reducing precipitate was prepared by varying the content of the vanadium compound (V ₂ 0 ₅ ) and the manganese compound (MnS0 ₄ · 5¾0) such that the molar ratio of the metal component was Mn: V = 0.85: 0.15. and a cathode active material for a lithium secondary battery in the same manner _{_{_{[Li 4/3 (Mn 0}}} . 85 V 0. 15) 2/3 0 2] for manufacturing and using the SEM, XRD in the same manner was confirmed to particle size and structure.

Example 4

Vanadium compound (V ₂ 0 ₅₎ instead of the niobium compound (Nb ₂ 0 ₅₎ in Example 1, ^and, for a lithium secondary battery positive electrode active material in the same manner except that the amorphous phase is prepared by using the reduction precipitate [Li _4/3 _{_{_{(Mno. 95 Nb 0. 05}}} ) 2/3 0 2] for manufacturing and using the SEM, XRD in the same manner was confirmed to particle size and structure.

Example 5

The amount of niobium compound (Nb ₂ 0 ₅ ) and manganese compound (MnS0 ₄ · 5¾0) was changed to ^' except that the amorphous reduced precipitate was prepared by varying the molar ratio of the metal component to Mn: Nb = 0.9: 0.1. In the same manner as in Example 4, a cathode active material [L ^ Mno.sNbo.i) ^^ for a lithium secondary battery was prepared, and the particle size and structure were confirmed using SEM and XRD in the same manner.

Example 6

Niobium compound (Nb ₂ 0 ₅₎ and the molar ratio of the content of a manganese compound (MnS0 ₄ .5¾0) metal Mn: Nb = 0.85: Example 4, except that the amorphous phase is reduced to prepare a precipitate by changing to 0.157} to prepare a cathode active material for a lithium secondary battery _{_{[Li 4/3 (Mno. 85 Nb}} 0. 15) 2/3 0 2] in the same manner as in the same way using a SEM, XRD was confirmed the particle size and structure. Comparative Example 1

Wet process (wet process; solution-based precipi tat ion) ° 1 solid process (solid-state react ion) in the same composition as in Example 1 lithium secondary battery positive electrode active material [Li _4/3 (Mn ₀ . _{_{_{_{95 V 0. 05) 2/3 0}}}} 2] was prepared.

First, a lithium compound (Li ₂ CO ₃ ), a vanadium compound (V ₂ 0 ₅ ), and a manganese compound (Mn ₂ 0 ₃ ) were mixed. At this time, the molar ratio (Li / Metal ratio) of lithium to manganese was set to 2.04, and vanadium 0.05 η) 1 was mixed. Then a 10 mm ball. Planetary ball milling was used to obtain a uniform lithium manganese vanadium complex mixture.

The obtained lithium manganese vanadium composite mixture was placed in a tube furnace, heated up at a rate of 3 ^° C. per minute to raise the temperature to 650 ^° C., and then maintained in this state while applying oxygen gas for 20 hours. Was carried out. This process, the black red cathode active material for a lithium secondary battery in accordance with the invention by carrying out _{_{_{[Li 4/3 (Mn 0. 95}}} V 0. 05) 2/3 0 2] After producing the dry process, as in Example 1, In the same manner, the particle size and structure were confirmed using SEM and XRD.

Comparative Example 2

Content of Vanadium Compound (V ₂ 0 ₅ ) and Manganese Compound (Mn ₂ 0 ₃ ) Lithium secondary in the same manner as in Comparative Example 1, except that the molar ratio of all metal components is Mn: V = 0.9: 0.1 A battery positive electrode active material [L Mno.gVo ^ O] was prepared and the particle size and structure were confirmed using SEM and XRD in the same manner.

Comparative Example 3

Vanadium compound (V ₂ 0 ₅₎ instead of the niobium compound (Nb ₂ 0 _5), and a is, in Comparative Example 1 and a lithium secondary battery positive electrode active material in the same way except that _{_{_{[Li 4/3 (Mn 0. 95}}} Nb 0. ₀₅ ) _2/3 0 ₂ ] were prepared and the particle size and structure were confirmed by using the SEM, XRD in the same manner.

Comparative Example 4

Lathium in the same manner as in Comparative Example 4 except that the content of niobium compound (Nb ₂ 0 ₅ ) and manganese (Mn ₂ 0 ₃ ) was changed so that the molar ratio of the metal component was Mn: Nb = 0.9: 0.1 Positive electrode active material for secondary batteries [L /^Mno.gNbo.^/sOs] Prepared and confirmed the particle size and structure using SEM, XRD in the same manner. Comparative Example 5

Contents of the vanadium compound (V ₂ 0 ₅ ) and the manganese compound (Mn ₂ 0 ₃ ) A lithium secondary in the same manner as in Comparative Example 1, except that the molar ratio of all metal components was Mn: V = 0.85: 0.15 battery positive electrode active material _{_{_{[Li 4/3 (Mn 0}}} . 85 V 0. 15) 2/3 0 2] for manufacturing and using the SEM, XRD in the same manner was confirmed to particle size and structure. However, the cathode active material prepared as described above did not proceed to measure electrochemical properties because of impurities.

Comparative Example 6

Lithium secondary in the same manner as in Comparative Example 4 except that the content of niobium compound (Nb ₂ 0 ₅ ) and manganese compound (Mn ₂ 0 ₃ ) was changed such that the molar ratio of the metal component was Mn: Nb = 0.85: 0.15 battery positive electrode active material _{_{_{[Li 4/3 (Mn 0. 85}}} Nb 0. 15) 2/3 0 2] for manufacturing and using the SEM, XRD in the same manner was confirmed to particle size and structure. Test Example

After producing the half-cell lithium secondary battery using the positive electrode active material prepared according to Examples 1 to 6 and Comparative Examples 1 to 6 in the following manner, battery performance evaluation was performed. a) lithium secondary battery manufacturing

The positive electrode active material powders prepared according to Examples 1 to 6 and Comparative Examples 1 to 6 were classified so as to have an average particle diameter of 20. A slurry was prepared using 80 wt% of the positive electrode material, 10 wt% of acetylene black as the conductive agent, and 10% PVdF as the binder, using NMP as the solvent. The slurry was applied to an aluminum foil (Al foil) having a thickness of 20 / ΛΠ, dried and compacted by a press, and dried for 16 hours at 120 ^° C. in a vacuum to prepare a positive electrode in the form of a disc having a diameter of 16 mm.

The cathode was a lithium metal foil punched to 16 mm in diameter, and a PP film was used as the separator. As an electrolyte solution, a mixed solution of EC / EMC 1: 2 v / v of 1 M LiPF ₆ was used. After impregnating the electrolyte into the separator, insert the separator between the positive electrode and the negative electrode, and then replace the case of stainless steel (SUS) product. A test cell for covering the electrode, that is, a lithium secondary battery half cell was manufactured. b) battery performance evaluation

By the method as described above, for a half-cell lithium secondary battery prepared using the positive electrode 5 active material according to Examples 1 to 6 and Comparative Examples 1 to 6, to analyze the capacity and efficiency of repeated use of layer discharge The experiment was conducted. In other words, a current of 10 mAg ¹ was applied using a charger and discharger to 1 · 5 to 4.8 V. Thus, after repeatedly using the lithium secondary battery to fully charge and discharge, an experiment was conducted to compare and analyze the capacity according to the number of repeated use. In addition, the life characteristics measurement results for the lithium secondary battery using the positive electrode active according to Examples 1 to 3 and Comparative Examples 1 to 4 are as shown in Table 1 below.

Table 1

As shown in Table 1, the lithium secondary battery including the positive electrode active material of Examples 1 to 3 prepared using the reduced precipitated precursor has a high discharge efficiency. To be used as an excellent sole cathode material. It was confirmed that there was no problem at all. In particular, in the case of the lithium secondary battery according to Examples 1 to 3, it can be seen that the result of the remarkably improved retention of the maximum discharge capacity according to the increase in the amount of vanadium doping.

On the other hand, it was confirmed that the lithium secondary battery including the cathode active material of Comparative Examples 1 to 4 prepared in the discharge capacity measurement results in the progress of life as in the past did not satisfy these characteristics. In particular, it can be seen that the lithium secondary batteries according to Comparative Examples 2 and 4 have a significant drop in the discharge capacity due to the increase in the vanadium composition, resulting in a change in the manganese oxide number with the progress of a long life, and thus, a problem in maintaining the crystal structure. In addition, it can be seen that the lithium secondary batteries according to Comparative Examples 3 and 4 are not good at improving the discharge capacity of the electrochemical characteristic measurement results according to the niobium composition change, and thus there is a limit to using them alone. On the other hand, each of the lithium-manganese composite oxide prepared by the dry process according to the reduction precipitation method, and Comparative Example 2 according to the second embodiment of the present invention _{_{_{[Li 4/3 (Mn 0. 90}}} V 0. 10) 2/3 0 2] The SEM measurement results measured after further heat treatment at a high temperature are shown in FIG. 11 [(A) Example 2, (B) Comparative Example 2]. Here, the heat treatment was performed at 900 ^° C for 10 hours. When the SEM measurement result after the high temperature heat treatment of FIG. 11 is compared with FIG. 4, the SEM measurement result before the heat treatment, Example 2 prepared by the reduction precipitation method according to the present invention does not have large particle sizes even at 900 ^° C. heat treatment. It can be seen. However, in the case of Comparative Example 2 prepared by the dry method is 900 ^° at C heat-treating step of the grain growth confirmed that substantially takes place, and thus when the average particle diameter is too increased to inside the metal oxide particles followed by lithium diffusion ^■ As the distance increases, there may be a problem that the speed characteristic is degraded.

In addition, the XRD measurement after the heat treatment at a high temperature for the lithium manganese composite oxide prepared by the reduction precipitation method according to Examples 2 and 3 of the present invention and the lithium manganese composite oxide prepared by the dry method according to Comparative Example 2 The results are shown in FIG. Here, the heat treatment was performed at 900 ^° C for 10 hours. From the XRD measurement results graph of Figure 12, at 900 ^° C In the case of heat treatment, in Comparative Example 2 according to the dry method in V doping, impurities are formed, but it can be seen that impurities are not produced when the reduction precipitation method of Examples 2 and 3 is applied in V doping. That is, it can be seen that the solubility is better in the wet process (solution-based precipitation).

Claims

[Claim] The manganese complex precipitate by reduction precipitation of manganese and dissimilar metal elements from a mixed solution containing manganese compounds and heterometal compounds containing at least one dissimilar metal element selected from the group consisting of claims 11 V and Nb Generating a; And mixing the manganese composite precipitate and the lithium compound, and calcining under conditions of 300 to 800 ° C. to produce a lithium manganese composite oxide represented by Formula 1 below; Method for producing a cathode active material for a lithium secondary battery comprising:

[Formula 1]

Lii + aCMn! -BMb) ^

Wherein a is 0 <a <l / 3, b is 0 <b <0.5, and M is at least one metal element selected from the group consisting of V and Nb.

[Claim ² ]

The method of claim 1,

The lithium compound may be at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium sulfite, lithium fluoride, lithium nitrate, lithium bromide, lithium oxide, and lithium chloride. Way .

[Claim 3]

The method of claim 1,

The manganese compound is a method for producing a positive electrode active material for a lithium secondary battery is at least one selected from the group consisting of manganese sulfate, manganese nitrate, manganese acetate, manganese acetate, manganese chloride, manganese dioxide, manganese trioxide, and manganese tetraoxide.

[Claim 4]

The method of claim 1,

The dissimilar metal compound is vanadium metal, vanadium oxide, vanadium oxychloride, vanadium tetrachloride, vanadium trichloride, ammonium metavanadate, sodium metavanadate and potassium metavanadate, lithium chloride, niobium oxide, niobium chloride, and niobium phosphide Method for producing a positive electrode active material for lithium secondary batteries selected from the group consisting of.

[Claim 5]

According to claim 1,

The reduction precipitation step is a method for producing a cathode active material for a lithium secondary battery performed under the conditions of pH 9 to pH 13.

[Claim 6]

The method of claim 1,

The reduction precipitation step is performed by adding at least one reducing agent selected from the group consisting of KBH ₄ , LiBH ₄ , NaBH ₄ , NaAlH ₄ , and LiAlH ₄ to the mixed solution.

[Claim 7]

According to claim 1,

The manganese composite precipitate produced from the reduction precipitation step is an amorphous phase of the positive electrode active material for a lithium secondary battery.

[Claim 8]

The method of claim 1,

Method of producing a cathode active material for a lithium secondary battery to react so that the molar ratio of lithium to manganese is 1.60 to 1.80 rrol.

[Claim 9]

The method of claim 1,

A method of washing the lithium secondary battery positive electrode active material to react so that the molar ratio of the dissimilar metal element to manganese is 0.01 to 0.50 m.

[Claim 10]

According to claim 1, —

The firing step is a method of manufacturing a positive electrode active material for a lithium secondary battery performed by a two-step heat treatment process including a first heat treatment and a second heat treatment.

[Claim 11]

The method of claim 10,

The first heat treatment is carried out for 7 to 15 hours at a temperature of 300 to 700 ^° C. Performing by heating, the secondary heat treatment is a method of manufacturing a positive electrode active material for a lithium secondary battery is carried out by heating for 10 to 20 hours at a temperature of 300 to 800 ^° C after the first heat treatment.

[Claim 12]

The method of claim 1,

And dissolving the dissimilar metal compound in a basic solvent having a pH of 9 to 13, adjusting the pH to 2 to 6, and then dissolving a manganese compound to prepare a mixed solution.

[Claim 13]

The method of claim 1,

Method of producing a positive electrode active material for a lithium secondary battery further comprising the step of drying the manganese composite precipitate produced from the reduction precipitation step under the conditions of 40 to 150 ^° C.

[Claim 14]

A cathode active material for a lithium secondary battery manufactured by the method according to any one of claims 1 to 13.

[Claim 15]

The method of claim 14,

A cathode active material for a lithium secondary battery including a lithium manganese composite oxide represented by Formula 1 below:

[Formula 1]

Lii _{+ a} (fci— bMb ^ -aCfe

[Claim 16]

The method of claim 15,

The lithium manganese composite oxide is a cathode active material for a lithium secondary battery that is represented by the following formula (2):

. [Formula 2] _{_{Li 4/3 (Mni- x M}} x) 2/30 2

Wherein x is 0 ≦ x ≦ 0.5 and M is at least one metal element selected from the group consisting of V and Nb.

[Claim 17]

The method of claim 16,

The lithium manganese composite oxide is _{_{_{Li 4/3 (Mn 0. 95 V}}} 0. 05) 2/3 0 ^ L i 4/3 (Mn 0. 9 Vo .1) 2/302, L i 4/3 (Mn _{_{_{0. 85 V 0 .15) 2/302}}} , L i 4/3 (Mn 0. g 5 Nb 0 .05) 2 / 3O2,

Li tno.gNbo ^. ^ / ^ SO and _{_{_{Li 4/3 (Mn 0. 995 Nb}}} 0. 05) 2/3 0 ₂ is selected from the group consisting of at least one member for a lithium secondary battery positive electrode active material.

[Claim 18]

The method of claim 14,

A cathode active material for a lithium secondary battery having a discharge capacity of at least two cycles of 140 mAhg ^"1 or more.

[Claim 19]

A lithium secondary battery comprising the cathode active material according to claim 14.

[Claim 20]

The method of claim 19,

A cathode including a cathode active material;

An anode including a negative electrode active material; And

Separator between anode and cathode

Lithium secondary battery comprising a.