JP6848172B2 - Material with lithium composite metal oxide part, intermediate part and conductive oxide part - Google Patents

Description

The present invention relates to a material having a lithium composite metal oxide portion, an intermediate portion and a conductive oxide portion.

The active material of the lithium ion secondary battery has been known that various materials are used, of which the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr , Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V. The lithium composite metal oxide represented by 1.7 ≦ f ≦ 3) is widely used as an active material for a lithium ion secondary battery.

In recent years, research based on the above-mentioned lithium composite metal oxide has been actively conducted in order to provide a more excellent active material.

For example, Patent Document 1 and Patent Document 2 describe a method for producing the above-mentioned lithium composite metal oxide in which various production parameters are specified. Further, Patent Document 2 also describes a method for producing a lithium composite metal oxide in which D is Zr in the above general formula.

Japanese Unexamined Patent Publication No. 2012-018827 Japanese Unexamined Patent Publication No. 2012-256435

However, the demand for active materials for lithium ion secondary batteries is increasing, and the provision of new lithium composite metal oxides that can be better active materials is eagerly desired.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a new material that can be an active material and a method for producing the same.

As a result of diligent studies by the present inventor, we have succeeded in forming a conductive oxide portion on the surface of the lithium composite metal oxide by a specific production method. Furthermore, the present inventor has found that the material obtained by such a production method can function as an active material such as a secondary battery.

As a result of further diligent studies, the present inventor has succeeded in producing a material in which a specific metal compound is interposed between the lithium composite metal oxide and the conductive oxide portion, and the material is more suitable. The present invention was completed by finding that it can function as an active material such as a secondary battery.

Material of the present invention have the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, At least one element selected from Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3). ,
On the surface of the lithium composite metal oxide portion, an intermediate portion containing Zr and / or Al and an intermediate portion
It is characterized by having a conductive oxide portion on the surface of the intermediate portion.

INDUSTRIAL APPLICABILITY According to the present invention, a new material that can be an active material can be provided.

8 is an SEM image of a lithium composite metal oxide having an intermediate precursor on the surface, which was obtained in step e) of Example 1. It is an SEM image of the material of Example 1. It is an SEM image of the material of Comparative Example 1. It is an SEM image of the material of Comparative Example 2. It is an SEM image of the lithium composite metal oxide of Reference Production Example 1.

The best mode for carrying out the present invention will be described below. Unless otherwise specified, the numerical range "x to y" described in the present specification includes the lower limit x and the upper limit y. Then, a numerical range can be constructed by arbitrarily combining these upper and lower limit values and the numerical values listed in the examples. Further, the numerical value arbitrarily selected from the numerical range can be set as the upper limit value and the lower limit value.

Material of the present invention have the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, At least one element selected from Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3). ,
On the surface of the lithium composite metal oxide portion, an intermediate portion containing Zr and / or Al and an intermediate portion
It is characterized by having a conductive oxide portion on the surface of the intermediate portion.

Further, in the method for producing a material of the present invention, a lithium composite metal oxide portion, an intermediate portion containing Zr and / or Al on the surface of the lithium composite metal oxide portion, and a conductive oxidation on the surface of the intermediate portion. It is a method of manufacturing a material having a material part, and is
a) general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, Ru, Sc, A step of preparing a lithium composite metal oxide represented by at least one element selected from Sn, In, Y, Bi, S, Si, Na, K, P and V, 1.7 ≦ f ≦ 3).
b) A step of preparing a first metal aqueous solution containing Zr and / or Al as a raw material for the intermediate portion.
c) A step of preparing a second metal aqueous solution as a raw material for the conductive oxide portion,
d) A step of preparing a first dispersion liquid in which the lithium composite metal oxide is dispersed in water.
e) A step of mixing the first dispersion liquid and the first metal aqueous solution to obtain a first mixed dispersion liquid, and adhering an intermediate precursor to the surface of the lithium composite metal oxide.
f) The step of preparing a second dispersion liquid in which the lithium composite metal oxide having the intermediate precursor on the surface is dispersed in water, or the step of heating the lithium composite metal oxide having the intermediate precursor on the surface. A step of preparing a second dispersion liquid in which a lithium composite metal oxide having an intermediate portion on the surface is dispersed in water.
g) A step of mixing the second dispersion liquid and the second metal aqueous solution to obtain a second mixed dispersion liquid, and adhering a conductive oxide precursor to the intermediate portion precursor or the surface of the intermediate portion.
h) The step of heating the lithium composite metal oxide that has undergone the g) step,
It is characterized by having.

Hereinafter, the present invention will be described along with the method for producing the material of the present invention. Unless otherwise specified, the pH specified in the present specification refers to a value measured at 25 ° C.

First, a) a step will be described. a) step of the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re , Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, Ru , Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V. At least one element, 1.7 ≦ f ≦ 3), prepares a lithium composite metal oxide. It is a process.

General _{formula: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, In at least one element selected from Bi, S, Si, Na, K, P, and V, 1.7 ≦ f ≦ 3), the values of b, c, and d are particularly high as long as they satisfy the above conditions. There is no limitation, but 0 <b <1, 0 <c <1, 0 <d <1 is preferable, and at least one of b, c, and d is 10/100 <b <90/100. It is preferably in the range of 10/100 <c <90/100, 5/100 <d <70/100, 12/100 <b <80/100, 12/100 <c <80/100, 10 / More preferably, the range is 100 <d <60/100, and the range is 15/100 <b <70/100, 15/100 <c <70/100, 12/100 <d <50/100. Is even more preferable.

The values a, e, and f may be values within the range specified by the general formula, preferably 0.5 ≦ a ≦ 1.5, 0 ≦ e <0.2, 1.8 ≦ f ≦ 2.5. , More preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, 1.9 ≦ f ≦ 2.1 can be exemplified.

The lithium composite metal oxide can be produced according to a known production method using a metal salt such as a metal oxide, a metal hydroxide, or a metal carbonate. The lithium composite metal oxide is produced, for example, by firing its precursor at 750 ° C. or higher, and by such firing, the arrangement of the elements constituting the lithium composite metal oxide shows a layered rock salt structure. ..

The lithium composite metal oxide can be produced as follows, for example, when lithium carbonate, nickel sulfate, manganese sulfate and cobalt sulfate are used (coprecipitation method). An aqueous sulfate solution containing a predetermined amount of nickel sulfate, cobalt sulfate and manganese sulfate is made alkaline to obtain a co-precipitated slurry, which is dried to obtain a nickel cobalt-manganese composite hydroxide. A lithium composite metal oxide having a layered rock salt structure can be obtained by mixing a predetermined amount of lithium carbonate with the nickel-cobalt-manganese composite hydroxide and firing at 750 ° C. or higher. The above firing may be a multi-step method of firing under a plurality of temperature conditions.

The lithium composite metal oxide may be appropriately pulverized to form a powder, and may be further classified into a desired particle size. As for the range of the particle size distribution of the lithium composite metal oxide, the average particle size (D50) is preferably 100 μm or less, more preferably 1 μm or more and 50 μm or less, and 1 μm or more in the measurement with a general laser scattering diffraction type particle size distribution meter. It is more preferably 30 μm or less, and particularly preferably 2 μm or more and 20 μm or less.

In addition, the lithium composite metal oxide is prepared by a solid phase method or a spray-drying method with respect to a mixed raw material composed of a lithium raw material containing Li and a metal raw material containing at least one selected from Ni, Mn and Co. , It can be produced by using a known method such as a hydrothermal method or a molten salt method.

The solid-phase method is a method of obtaining a lithium composite metal oxide by mixing and / or pulverizing a powder of a mixed raw material, drying and / or molding as necessary, and then heating and firing. The solid-phase method, which is usually performed, is performed by mixing each raw material at a ratio according to the composition of the lithium composite metal oxide to be produced. The heating temperature of the raw material mixture in the solid phase method is preferably 900 ° C. or higher and 1000 ° C. or lower, and the heating time is preferably 8 hours or longer and 24 hours or lower.

The spray-drying method is a method in which powder of a mixed raw material is dissolved in a liquid to form a solution, and the solution is sprayed into the air to form a mist, and the mist-based solution is heated. The powder obtained by the spray-drying method may be additionally heated. The heating temperature in the spray-drying method is preferably 500 ° C. or higher and 1000 ° C. or lower, and the heating time is preferably 3 hours or longer and 8 hours or lower.

The hydrothermal method is a method in which a raw material is mixed with water to form a mixed solution, and the mixed solution is heated under high temperature and high pressure. The heating temperature in the hydrothermal method is preferably 120 ° C. or higher and 200 ° C. or lower, and the heating time is preferably 2 hours or longer and 24 hours or lower.

The molten salt method is a method in which a lithium compound is melted into a molten salt by heating a raw material mixture containing a lithium compound, and a lithium composite metal oxide is synthesized in this molten liquid. The molar ratio of Li of the lithium composite metal oxide to be produced to Li of the lithium compound to be used (Li of the lithium composite metal oxide to be produced / Li of the lithium compound) may be less than 1, but 0.02. It is preferably less than 0.7, and more preferably 0.03 to 0.5 and 0.04 to 0.25.

D in the above general formula is a doping element. As the doping element, Ti, Zr, Hf, and Rf are preferable, and Zr is particularly preferable. When preparing a lithium composite metal oxide in the range of 0 <e <1 in the above general formula, a dope element-containing compound may be added at any stage of producing the above lithium composite metal oxide. .. The blending amount of the doping element-containing compound may be appropriately determined so as to obtain a desired doping amount.

Next, b) step will be described. b) The step is a step of preparing a first metal aqueous solution containing Zr and / or Al as a raw material for the intermediate portion.

The concentration of the first metal aqueous solution is not particularly limited, but an aqueous solution containing about 0.001 to 0.01 mol of Zr ion and Al ion with respect to 1 mol of the lithium composite metal oxide used is preferable. The first metal aqueous solution may contain a metal other than Zr and Al.

To prepare the first metal aqueous solution, a metal salt containing Zr and / or Al may be dissolved in water. Examples of the metal salt include sulfates, carbonates, nitrates, acetates, phosphates, halides, and hydrates thereof. If the solubility of the metal salt in water is low, an acid may be added.

The first metal aqueous solution may contain a hetero element-containing organic compound. The hetero element in the hetero element-containing organic compound means N, O, P or S. Examples of the hetero element-containing organic compound include an amino group, an amide group, an imide group, an imino group, a cyano group, an azo group, a hydroxyl group, an alkoxy group, a carboxyl group, an ester group, an ether group, and a carbonyl group, which can be coordinated with a metal ion. Phosphoic acid group, phosphoric acid ester group, phosphonic acid group, phosphonic acid ester group, phosphinic acid group, phosphinic acid ester group, phosphenic acid group, phosphenic acid ester group, phosphenic acid group, phosphenic acid ester group, thiol group, Examples thereof include organic compounds having a sulfide group, a sulfinyl group, a sulfonyl group, a sulfonic acid group, a thiocarboxyl group, a thioester group or a thiocarbonyl group.

In particular, as the hetero element-containing organic compound, a chelate compound having a plurality of the above groups and capable of coordinating with a metal ion at a plurality of locations is preferable.

Specific examples of chelate compounds include polyamine compounds such as ethylenediamine and diethylenetriamine, amino acids such as glycine, alanine, cysteine, glutamine, arginine, asparagine, aspartic acid, serine and ethylenediamine tetraacetic acid, malonic acid, succinic acid, glutaric acid and malein. Dicarboxylic acids such as acid and phthalic acid, glycolic acid, lactic acid, tartron acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitrate, leucine Hydroxycarboxylic acids such as acids, mevalonic acids, pantoic acids, quinic acids, shikimic acids, salicylic acids, gentidic acids, orseric acids, mandelic acids, benzylic acids and 2-hydroxy-2-phenylpropionic acid can be mentioned.

As the chelate compound added to the first metal aqueous solution, hydroxycarboxylic acid is particularly preferable. All of the above-mentioned specific hydroxycarboxylic acids can form a conformation in which an _{OH group and a CO 2 H group can be coordinated to the same metal ion.} The blending ratio of the metal salt containing Zr and / or Al and the hydroxycarboxylic acid in the first aqueous metal solution is preferably in the range of metal: hydroxycarboxylic acid = 1: 1 to 1: 3 in terms of molar ratio.

Next, the c) step will be described. c) The step is a step of preparing a second metal aqueous solution as a raw material for the conductive oxide portion.

In the production method of the present invention, the conductive oxide precursor is attached to the intermediate portion precursor or the surface of the intermediate portion in step g). Here, the conductive oxide precursor contains a metal hydroxide as a main component. More specifically, in the g) step, a metal hydroxide having low solubility is precipitated in the basic second mixed dispersion, and the metal hydroxide is the intermediate precursor or the surface of the intermediate. The phenomenon of adhering to the metal occurs.

Therefore, the second metal aqueous solution in step c) needs to contain a metal hydroxide that is sparingly soluble in water or a metal ion that can be a metal hydroxide that is sparingly soluble in water at a specific pH. Examples of the metal of the second metal aqueous solution include all metals other than alkali metals and all metals other than Zr and Al contained in the first metal aqueous solution. In general, metals other than alkali metals tend to exist as metal ions in a solution state in an acidic aqueous solution, and tend to precipitate as metal hydroxides in a strongly alkaline aqueous solution.

The second metal aqueous solution may contain one kind of metal ion or may contain a plurality of kinds of metal ions. The concentration of the second metal aqueous solution is not particularly limited, but a metal aqueous solution containing about 0.001 to 0.01 mol of metal ions with respect to 1 mol of the lithium composite metal oxide used is preferable. The second metal aqueous solution may contain an alkali metal.

Further, in step c), one kind of second metal aqueous solution may be prepared, or a plurality of second metal aqueous solutions containing different metal ions may be prepared.

For reference, the solubility products of typical metal hydroxides are shown in Table 1. It can be said that these metal hydroxides are sparingly soluble in water.

To prepare the second metal aqueous solution, a metal salt containing the desired metal may be dissolved in water. Examples of the metal salt include sulfates, carbonates, nitrates, acetates, phosphates, halides, and hydrates thereof. If the solubility of the metal salt in water is low, an acid may be added.

The second metal aqueous solution in which the metal salt is dissolved in water is usually a strongly acidic aqueous solution having a pH of about 1 to 3.

The aqueous solution of the second metal may contain an organic compound containing a hetero element. The hetero element in the hetero element-containing organic compound means N, O, P or S. Examples of the hetero element-containing organic compound include an amino group, an amide group, an imide group, an imino group, a cyano group, an azo group, a hydroxyl group, an alkoxy group, a carboxyl group, an ester group, an ether group, and a carbonyl group, which can be coordinated with a metal ion. Phosphoic acid group, phosphoric acid ester group, phosphonic acid group, phosphonic acid ester group, phosphinic acid group, phosphinic acid ester group, phosphenic acid group, phosphenic acid ester group, phosphenic acid group, phosphenic acid ester group, thiol group, Examples thereof include organic compounds having a sulfide group, a sulfinyl group, a sulfonyl group, a sulfonic acid group, a thiocarboxyl group, a thioester group or a thiocarbonyl group.

In particular, as the hetero element-containing organic compound, a chelate compound having a plurality of the above groups and capable of coordinating with a metal ion at a plurality of locations is preferable.

Specific examples of chelate compounds include polyamine compounds such as ethylenediamine and diethylenetriamine, amino acids such as glycine, alanine, cysteine, glutamine, arginine, asparagine, aspartic acid, serine and ethylenediamine tetraacetic acid, malonic acid, succinic acid, glutaric acid and malein. Dicarboxylic acids such as acid and phthalic acid, glycolic acid, lactic acid, tartron acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitrate, leucine Hydroxycarboxylic acids such as acids, mevalonic acids, pantoic acids, quinic acids, shikimic acids, salicylic acids, gentidic acids, orseric acids, mandelic acids, benzylic acids and 2-hydroxy-2-phenylpropionic acid can be mentioned.

By containing the hetero element-containing organic compound in the second metal aqueous solution containing a plurality of types of metal ions, it is possible to simultaneously precipitate a plurality of types of metal hydroxides in step g).

As described above, the second metal aqueous solution is usually a strongly acidic aqueous solution having a pH of about 1 to 3, but in the second metal aqueous solution containing a hetero element-containing organic compound, the solubility of metal ions is high, so the pH is set to 4 to 4. It may be within the range of 6.

Next, d) the step will be described. d) The step is a step of preparing a first dispersion liquid in which a lithium composite metal oxide is dispersed in water. The first dispersion may be prepared by mixing 1 to 100 parts by mass, preferably 2 to 50 parts by mass of water with respect to 1 part by mass of the lithium composite metal oxide.

Generally, a dispersion in which a lithium composite metal oxide is dispersed in water is extremely alkaline. Therefore, in step e), when the first metal aqueous solution prepared in step b) is added dropwise to the remarkably strong alkaline first dispersion prepared in step d) to form the first mixed dispersion, the first metal aqueous solution is obtained. The contained Zr ion and / or Al ion is immediately precipitated as a hydroxide. Even in this case, the intermediate precursor containing zirconium hydride and / or aluminum hydroxide as a main component may adhere to the surface of the lithium composite metal oxide, but the precipitation of zirconium hydride and / or aluminum hydroxide is the first. Since it can occur everywhere in the mixed dispersion, a large amount of zirconium hydride and / or aluminum hydroxide that does not adhere to the surface of the lithium composite metal oxide will be present, and also to the surface of the lithium composite metal oxide. The adhesion of the intermediate precursor of the above may be uneven.

Therefore, it is preferable that the pH of the first dispersion liquid in step d) is adjusted by adding an acid. As the acid to be added, a weak acid is preferable because it can suppress a significant fluctuation in pH due to a buffering action. Examples of the weak acid include acetic acid, formic acid, oxalic acid, phosphoric acid, carbonic acid, and boric acid. As a suitable pH of the first dispersion liquid, the range of 3 to 11 can be exemplified.

If the pH is an acidic first dispersion, even if the first dispersion is mixed with the first metal aqueous solution prepared in step b) in step e), hydroxide does not immediately precipitate. Therefore, by appropriately controlling the pH in step e), the intermediate precursor can be uniformly attached to the surface of the lithium composite metal oxide.

In the case of the first dispersion having a pH of 7 to 11, when the first dispersion and the first metal aqueous solution prepared in step b) are mixed in step e), the surface of the lithium composite metal oxide starts to precipitate. Alternatively, the intermediate precursor is likely to be deposited in an orderly manner as a nuclear generation site.

Next, the e) step will be described. e) The step is a step of mixing the first dispersion liquid and the first metal aqueous solution to obtain the first mixed dispersion liquid, and adhering the intermediate precursor to the surface of the lithium composite metal oxide. Here, the intermediate precursor is mainly composed of zirconium hydride and / or aluminum hydroxide. From a chemical point of view, the e) step will be specifically described. In the e) step, zirconium hydride and / or aluminum hydroxide having low solubility in a basic aqueous solution is precipitated mainly by pH control, and then A phenomenon occurs in which these hydroxides adhere to the surface of the lithium composite metal oxide.

The pH of the first mixed dispersion is preferably 8 or more, and 9 to 13 can be exemplified as a preferable pH range. When a first metal aqueous solution containing a hetero element-containing organic compound is used, the pH of the first mixed dispersion is preferably 12 or more, more preferably 13 or more. The pH value of the first mixed dispersion in step e) means the value of the first mixed dispersion measured with a pH meter.

If the pH of the first dispersion is originally 8 or more, in step e), a basic aqueous solution is appropriately added to the first mixed dispersion so that the pH of the first mixed dispersion does not become less than 8, and the pH is adjusted. You may adjust. For example, the basic aqueous solution may be added at the same time as the first metal aqueous solution is added to the first dispersion.

In order to mix the first dispersion liquid and the first metal aqueous solution to obtain the first mixed dispersion liquid, it is preferable to add the first metal aqueous solution to the first dispersion liquid. A preferred addition rate of the first metal aqueous solution is 10 to 1000 mL / h, a more preferable addition rate is 20 to 500 mL / h, and a further preferable addition rate is 50 to 300 mL / h.

e) A basic aqueous solution is used for pH control in the step. The pH of the basic aqueous solution is preferably in the range of 9 to 14, more preferably in the range of 10 to 14, and even more preferably in the range of 11 to 14. A basic aqueous solution is prepared by dissolving a basic compound in water. The basic compound that can be used may be one that dissolves in water and exhibits basicity. For example, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, sodium carbonate, potassium carbonate, and the like. Alkali metal carbonates such as lithium carbonate, alkali metal phosphates such as trisodium phosphate, tripotassium phosphate, trilithium phosphate, alkali metal acetates such as sodium acetate, potassium acetate and lithium acetate, and ammonia. Can be done. The basic compound may be used alone or in combination of two or more.

When zirconium hydride and / or aluminum hydroxide is precipitated by adding the basic aqueous solution to the first mixed dispersion, the addition rate of the basic aqueous solution should be slow. A preferred addition rate of 10 to 1000 mL / h, a more preferable addition rate of 20 to 500 mL / h, and a more preferable addition rate of 50 to 300 mL / h can be exemplified.

e) The step is preferably carried out under stirring conditions. Further, the first mixed dispersion may be cooled or heated for the purpose of promoting the precipitation of zirconium hydride and / or aluminum hydroxide.

Next, the f) step will be described. f) The step is a step of preparing a second dispersion liquid in which a lithium composite metal oxide having the intermediate precursor on the surface is dispersed in water, or a step of preparing a lithium composite metal oxide having the intermediate precursor on the surface. This is a step of preparing a second dispersion liquid in which a lithium composite metal oxide having an intermediate portion on the surface, which is produced by heating the above, is dispersed in water.

Of the steps f), the step of preparing the second dispersion liquid in which the lithium composite metal oxide having the intermediate precursor on the surface is dispersed in water may be a step that also serves as the step e) (in this case). F) The step is substantially included in the e) step. ) And e) After the step, a filtration step and a washing step if necessary are carried out to isolate a lithium composite metal oxide having an intermediate precursor on the surface, and the lithium composite metal oxide is dispersed in water again. It may be a process.

f) In the step, prepare a second dispersion liquid in which the lithium composite metal oxide having an intermediate portion on the surface is dispersed in water, which is produced by heating the lithium composite metal oxide having the intermediate portion precursor on the surface. Regarding the steps, e) after the step, a filtration step and a washing step if necessary are carried out to isolate a lithium composite metal oxide having an intermediate precursor on the surface, and further, the lithium composite metal oxide is heat-treated. Then, the lithium composite metal oxide that has undergone the step of changing the intermediate portion precursor to the intermediate portion may be dispersed in water. By heat treatment, zirconium hydride and / or aluminum hydroxide is dehydrated to zirconium oxide and / or aluminum oxide.

If necessary, the pH of the second dispersion in step f) may be adjusted by adding an acid or a base.

Next, the g) step will be described. g) The step is a step of mixing the second dispersion liquid and the second metal aqueous solution to obtain a second mixed dispersion liquid, and adhering the conductive oxide precursor to the intermediate portion precursor or the surface of the intermediate portion. As described above, in the g) step, a metal hydroxide having low solubility is precipitated in the basic second mixed dispersion, and the metal hydroxide is the intermediate precursor or the surface of the intermediate. The phenomenon of adhering to the metal occurs.

In order to mix the second dispersion liquid and the second metal aqueous solution to obtain the second mixed dispersion liquid, it is preferable to add the second metal aqueous solution to the second dispersion liquid. When the second dispersion is extremely alkaline, the rate of addition of the second metal aqueous solution should be slow. A preferred addition rate of the second metal aqueous solution is 10 to 1000 mL / h, a more preferable addition rate is 20 to 500 mL / h, and a further preferable addition rate is 50 to 300 mL / h.

c) When there are a plurality of second metal aqueous solutions prepared in the step, the plurality of second metal aqueous solutions may be added to the second dispersion liquid at the same time, or may be added separately. When a plurality of second metal aqueous solutions are added separately, one second metal aqueous solution is added to the second dispersion liquid to prepare a mixed dispersion liquid, and a conductive oxide precursor is formed on the intermediate portion precursor or the surface of the intermediate portion. Each conductive oxide precursor can be formed in layers by adding another second metal aqueous solution after adhering the body. That is, by repeating the g) step, a plurality of conductive oxide precursor layers can be formed. In this case, a filtration step and a cleaning step may be carried out for each g) step.

g) A basic aqueous solution is used when pH control in the step is required. As the basic aqueous solution, the one described in step e) may be appropriately used.

g) The step is preferably carried out under stirring conditions. Further, the second mixed dispersion may be cooled or heated for the purpose of promoting the precipitation of the metal hydroxide.

The lithium composite metal oxide having the conductive oxide precursor adhered to the intermediate portion precursor or the surface of the intermediate portion is separated through, for example, a filtration step, a washing step, and / or a drying step. The temperature of the drying step is preferably 80 to 200 ° C., more preferably 90 to 140 ° C., and even more preferably 100 to 130 ° C. Since the drying step can also be combined with the heating in the h) step, it may be omitted.

Next, the h) step will be described. The h) step is a step of heating the lithium composite metal oxide that has undergone the g) step, and is a step of chemically synthesizing the material of the present invention. Specifically, the intermediate portion precursor containing zirconium hydride and / or aluminum hydroxide as a main component and the conductive oxide precursor containing a metal hydroxide as a main component are dehydrated, and the intermediate portion and the conductive oxide are dehydrated. This is a part of the process. h) In the lithium composite metal oxide in which the intermediate portion is formed prior to the step, in the h) step, the conductive oxide precursor containing the metal hydroxide as a main component is dehydrated to form the conductive oxide portion. This is the process.

When a material in which no intermediate portion or intermediate portion precursor is present and only a conductive oxide precursor is present on the surface of the lithium composite metal oxide is heat-treated, the surface state of the material may change depending on the heating temperature. is there. It is presumed that the fluctuation is caused by the specific movement of a specific metal element (for example, lithium) constituting the lithium composite metal oxide portion to the surface of the material. In addition, it is presumed that the above fluctuations adversely affect the physical properties of the material as a positive electrode active material and the period of use.

However, in the method for producing a material of the present invention, since an intermediate portion or an intermediate portion precursor is present on the surface of the lithium composite metal oxide, a specific metal element specifically moves to the surface of the material even in the heat treatment. Is suppressed. Therefore, the physical properties of the material of the present invention as a positive electrode active material are excellent, and the period of use thereof is relatively long.

h) The heating temperature of the step is preferably 500 ° C. or higher, more preferably 500 to 1000 ° C., and even more preferably 600 to 800 ° C.

The heating time is preferably 0.5 to 20 hours, more preferably 1 to 15 hours, still more preferably 2 to 10 hours.

h) The step is carried out under atmospheric conditions.

h) The material of the present invention is formed through the steps. Further, it is preferable that the material of the present invention has a constant particle size distribution through a pulverization step and / or a classification step. As for the range of the particle size distribution, the average particle size (D50) measured by a general laser scattering diffraction type particle size distribution meter is preferably 100 μm or less, more preferably 1 μm or more and 50 μm or less, and further preferably 1 μm or more and 30 μm or less. It is particularly preferably 2 μm or more and 20 μm or less.

Material of the present invention have the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, At least one element selected from Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3). ,
On the surface of the lithium composite metal oxide portion, an intermediate portion containing Zr and / or Al and an intermediate portion
It has a conductive oxide portion on the surface of the intermediate portion.

The middle part is mainly composed of zirconium oxide and / or aluminum oxide. The intermediate portion is preferably formed on the entire surface of the lithium composite metal oxide portion. Further, the intermediate portion is preferably formed in a film shape. The thickness of the intermediate portion is preferably 0.1 to 20 nm, more preferably 0.5 to 10 nm, further preferably 1 to 5 nm, and particularly preferably 1 to 3 nm.

The conductive oxide portion means a portion containing a metal oxide and having higher conductivity than the lithium composite metal oxide portion.

The metal oxide contained in the conductive oxide portion means an oxide containing a metal contained in the second metal aqueous solution prepared in step c). For example, when the metal contained in the second metal aqueous solution prepared in step c) is La, the metal oxide contained in the conductive oxide portion corresponds to La oxide such as _{La 2} O _3.

Specific examples of the metal oxide include CaVO ₃ , MnO ₂ , La ₂ CuO ₄ , La ₂ NiO ₄ , SnO ₂ , Tl ₂ Mn ₂ O ₇ , EuO, Fe ₂ O ₃ , CamnO ₃ , SrMnO ₃ , and so on. (Sr, La) TiO ₃ , La TIM ₃ , SrFeO ₃ , BaMoO ₃ , CaMoO ₃ , Ln ₂ Os ₂ O ₇ , Tl ₂ Ir ₂ O ₇ , Cd ₂ Re ₂ O ₇ , Lu ₂ Ir ₂ O ₇ , Bi ₂ Rh ₂ O ₇ , Bi ₂ Ir ₂ O ₇ , Ti ₂ O ₃ , WO ₂ , VO, V ₂ O ₃ , LaMnO ₃ , CaCrO ₃ , LaCoO ₃ , (ZnO) ₅ , SrCrO ₃ , In _0.97 Y _{0 .03} O ₃ , Zn _x Al _y O (x + y = 1), LiV ₂ O ₄ , Na _1-x CoO ₂ (0 <x <1), LiTi ₂ O ₄ , SrMoO ₃ , BaPbO ₃ , Tl ₂ Os _{2 O 7, Pb 2 Os 2 O} 7, Pb 2 Ir 2 O 7, Lu 2 Ru 2 O 7, Bi 2 Ru 2 O 7, SrRuO 3, CaRuO 3, CrO 2, MoO 2, ReO 2, TiO, LaO, _{SmO, LaNiO 3, SrVO 3,} ReO 3, IrO 2, RuO 2, RhO 2, OsO 2, NdO, NbO, La 2 O 3, NiO, LaSr x Co y O 3 (x + y = 1), NaCoO 3, NaNiO ₃ , LiCoO ₃ , and LiNiO ₃ can be exemplified.

The metal oxide preferably has a crystal structure such as a perovskite type.

Here, considering that the material of the present invention can be used as an active material of a lithium ion secondary battery, the metal oxide contained in the conductive oxide portion is preferably one having excellent thermal stability. For _{example, LaSr x Co y O 3 (} x + y = 1) is excellent in thermal stability than LaNiO _3, it can be said that the preferred metal oxide.

The conductive oxide portion is preferably formed on the entire surface of the material of the present invention. Further, the conductive oxide portions may be formed in a film shape on the entire surface of the material of the present invention, may be scattered in an island shape, or may be formed in a state where crystals are projected. Good.

Examples of the range of the thickness t of the conductive oxide portion include 0 <t <200 nm, 0 <t <100 nm, and 0 <t <50 nm. Further, exemplifying the range of the major axis L of the crystal of the conductive oxide portion protruding from the surface of the material of the present invention is 0 <L <200 nm, 1 <L <150 nm, 5 <L <100 nm, 10 <L. <80 nm can be mentioned.

The material of the present invention can be used as an active material for a lithium ion secondary battery. The lithium ion secondary battery of the present invention comprises the material of the present invention as an active material. Specifically, the lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator having the material of the present invention as a positive electrode active material. In the material of the present invention, an intermediate portion containing Zr and / or Al is formed on the surface of the lithium composite metal oxide portion, and a conductive oxide portion is formed on the surface of the intermediate portion. Due to the presence of the intermediate portion and the conductive oxide portion, in the positive electrode provided with the material of the present invention as the positive electrode active material, the transition metal constituting the lithium composite metal oxide can be suppressed to some extent from elution from the positive electrode. Conceivable.

The positive electrode has a current collector and a positive electrode active material layer bonded to the surface of the current collector.

A current collector is a chemically inert electron conductor that keeps current flowing through the electrodes during the discharge or charging of a lithium-ion secondary battery. Collectors include at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel. Metallic materials can be exemplified. The current collector may be coated with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.

The current collector can take the form of foil, sheet, film, linear, rod, mesh or the like. Therefore, as the current collector, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless steel foil can be preferably used. When the current collector is in the form of a foil, a sheet, or a film, the thickness thereof is preferably in the range of 1 μm to 100 μm.

The positive electrode active material layer contains a positive electrode active material and, if necessary, a conductive auxiliary agent and / or a binder.

The positive electrode active material may be any material containing the material of the present invention, and only the material of the present invention may be adopted, or the material of the present invention and a known positive electrode active material may be used in combination.

Examples of known positive electrode active materials include _{spinel structure compounds such as LiMn 2} O ₄ , general formula: LiM _h PO ₄ (M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba). , Ti, Al, Si, B, Te and Mo, at least one element, an olivine structural compound represented by 0 <h <2), LiMVO ₄ or Li ₂ MSiO ₄ (M in the formula is Co, Ni , Mn, selected from at least one of Fe), a tabolite compound represented by LiMPO ₄ F (M is a transition metal), and LiMBO ₃ (M is a transition metal). Volarate compounds, Li ₂ MnO _{3, and the} like can be mentioned.

As the positive electrode active material used in combination with the material of the present invention, the above-mentioned olivine structure compound having a charge / discharge potential lower than that of the material of the present invention in a secondary battery is particularly preferable. When the olivine structure compound is present in the positive electrode active material layer of the secondary battery, the heat generation of the battery can be suppressed to some extent even when the positive electrode and the negative electrode are short-circuited. As the olivine structure compound, it is preferable to use a compound whose surface is carbon-coated.

The shape of the olivine structure compound is not particularly limited, but a compound having an average particle size smaller than that of the material of the present invention is preferable. The average particle size (D50) of the olivine structure compound in the measurement with a general laser scattering diffraction type particle size distribution meter is preferably 50 μm or less, more preferably 0.01 μm or more and 30 μm or less, and further preferably 0.1 μm or more and 10 μm or less. It is preferable, and 0.5 μm or more and 5 μm or less is particularly preferable.

The conductive auxiliary agent is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. The conductive auxiliary agent may be a chemically inert electron high conductor, which is carbon fine particles such as carbon black, acetylene black, Ketjen black (registered trademark), graphite, and vaporized carbon fiber (Vapor Grown Carbon). Fiber: VGCF), various metal particles, and the like are exemplified. These conductive auxiliary agents can be added to the active material layer alone or in combination of two or more.

The mixing ratio of the conductive auxiliary agent in the active material layer is preferably 1: 0.005 to 1: 0.5, and 1: 0.01 to 1: 0 in terms of mass ratio. It is more preferably .2, and even more preferably 1: 0.03 to 1: 0.1. This is because if the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer is deteriorated and the energy density of the electrode is lowered.

The binder serves to anchor the active material or the conductive auxiliary agent to the surface of the current collector and maintain the conductive network in the electrode. Examples of the binder include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins and poly ( Examples thereof include acrylic resins such as meta) acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose. These binders may be used alone or in combination of two or more.

The mixing ratio of the binder in the active material layer is preferably 1: 0.001 to 1: 0.3, preferably 1: 0.005 to 1: 0, in terms of mass ratio. It is more preferably .2, and even more preferably 1: 0.01 to 1: 0.15. This is because if the amount of the binder is too small, the moldability of the electrode is lowered, and if the amount of the binder is too large, the energy density of the electrode is lowered.

The negative electrode has a current collector and a negative electrode active material layer bonded to the surface of the current collector. As the current collector, the one described in the positive electrode may be appropriately adopted. The negative electrode active material layer contains a negative electrode active material and, if necessary, a conductive auxiliary agent and / or a binder.

Examples of the negative electrode active material include a carbon-based material capable of occluding and releasing lithium, an element capable of alloying with lithium, a compound having an element capable of alloying with lithium, and a polymer material.

Examples of the carbon-based material include graphitizable carbon, graphite, cokes, graphites, glassy carbons, calcined organic polymer compound, carbon fibers, activated carbon and carbon blacks. Here, the calcined product of an organic polymer compound refers to a product obtained by calcining a polymer material such as phenols or furans at an appropriate temperature to carbonize it.

Specific elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, and Si. , Ge, Sn, Pb, Sb, Bi can be exemplified, and Si or Sn is particularly preferable.

Specific examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , and NiSi ₂ . _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO can be exemplified, and in particular, SiO _x (0.3 ≦ x ≦ 1.6 or 0.5 ≦ x ≦ 1.5). Is preferable.

Among them, the negative electrode active material preferably contains a Si-based material having Si. The Si-based material is preferably composed of silicon and / or a silicon compound capable of occluding and releasing lithium ions, and for example, SiOx (0.5 ≦ x ≦ 1.5) is preferable. Although silicon has a large theoretical charge / discharge capacity, silicon has a large volume change during charge / discharge. Therefore, by using SiOx containing silicon as the negative electrode active material, it is possible to alleviate the volume change of silicon.

Further, the Si-based material preferably has a Si phase and a SiO ₂ phase. The Si phase is a phase composed of elemental silicon and capable of occlusion and release of Li ions, and expands and contracts with the occlusion and release of Li ions. The SiO ₂ phase is composed of SiO ₂ and serves as a buffer phase that absorbs the expansion and contraction of the Si phase. A Si-based material in which the Si phase is _{coated with the SiO 2 phase is preferable.} Further, it is preferable that a plurality of finely divided Si phases are _{coated with the SiO 2} phase to form particles integrally. In this case, the volume change of the entire Si-based material can be effectively suppressed.

_{The mass ratio of the SiO 2} phase to the Si phase in the Si-based material is preferably 1 to 3. If the mass ratio is too small, the expansion and contraction of the Si-based material becomes relatively large, and the negative electrode active material layer containing the Si-based material may be cracked. On the other hand, if the mass ratio is too large, the amount of occlusal and release of Li ions of the negative electrode active material is small, and the electric capacity per unit mass of the negative electrode of the battery is low.

Further, as a compound having an element capable of alloying with lithium, a tin compound such as a tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.) can be exemplified.

Specific examples of the polymer material include polyacetylene and polypyrrole.

As the negative electrode active material, a _{Si material obtained by heating layered polysilane obtained by treating CaSi 2} with an acid such as hydrochloric acid or hydrofluoric acid at 300 to 1000 ° C. may be adopted. Further, the Si material may be heated together with a carbon source and carbon-coated to be used as the negative electrode active material.

As the negative electrode active material, one or more of the above can be used.

As the conductive auxiliary agent and the binder used for the negative electrode, those described for the positive electrode may be appropriately and appropriately adopted in the same blending ratio.

In order to form an active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used to collect current. The active material may be applied to the surface of the body. Specifically, the active material, the solvent, and if necessary, the binder and / or the conductive auxiliary agent are mixed to prepare a slurry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The slurry is applied to the surface of the current collector and then dried. The dried one may be compressed in order to increase the electrode density.

The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

As the non-aqueous solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of the cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, vinylene carbonate, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which some or all of the chemical structure of the specific solvent is replaced with fluorine may be adopted.

Examples of the electrolyte include lithium salts such _{as LiClO 4} , LiAsF ₆ , LiPF _{6 , LiBF 4} , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) _2.

As the electrolytic solution, 0.5 mol / L to 1.7 mol of lithium salts such as _{LiClO 4} , LiPF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ are added to a non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate. An example of a solution dissolved at a concentration of about / L can be exemplified.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit due to contact between the two electrodes. Examples of the separator include polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, synthetic resin such as polyaramid (Aromatic polyamide), polyester and polyacrylonitrile, polysaccharides such as cellulose and amylose, and natural substances such as fibroin, keratin, lignin and sverin. Examples thereof include a porous body using one or more electrically insulating materials such as a polymer and ceramics, a non-woven fabric, and a woven fabric. Further, the separator may have a multi-layer structure.

Next, a method for manufacturing a lithium ion secondary battery will be described.

A separator is sandwiched between the positive electrode and the negative electrode as needed to form an electrode body. The electrode body may be any of a laminated type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a positive electrode, a separator and a negative electrode are wound. After connecting from the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collector lead or the like, an electrolytic solution is added to the electrode body to perform lithium ion secondary. Use a battery. Further, the lithium ion secondary battery of the present invention may be charged and discharged in a voltage range suitable for the type of active material contained in the electrode.

The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical type, a square type, a coin type, and a laminated type can be adopted.

The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium-ion secondary battery is mounted on a vehicle, a plurality of lithium-ion secondary batteries may be connected in series to form an assembled battery. In addition to vehicles, devices equipped with lithium-ion secondary batteries include various battery-powered home appliances such as personal computers and mobile communication devices, office devices, and industrial devices. Further, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydraulic power generation and other power storage devices and power smoothing devices for electric power systems, power supply sources for power and / or auxiliary machinery such as ships, aircraft, and aircraft. Power supply sources for spacecraft and / or auxiliary equipment, auxiliary power sources for vehicles that do not use electricity as power sources, power sources for mobile household robots, power sources for system backup, power sources for non-disruptive power supply devices, It may be used as a power storage device that temporarily stores the electric power required for charging in a charging station for an electric vehicle or the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. As long as it does not deviate from the gist of the present invention, it can be carried out in various forms with modifications, improvements, etc. that can be made by those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

(Example 1)
The material of Example 1 was produced as follows.

a) A lithium composite metal oxide represented by _{LiNi 5/10} Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

b) 0.11 g of zirconium sulfate and 0.065 g of glycolic acid as a hydroxycarboxylic acid were dissolved in 40 mL of water to prepare a first metal aqueous solution. In the first metal aqueous solution, the molar ratio of zirconium to glycolic acid was 1: 2.

c) Prepare a second metal aqueous solution in which 4.4 g of lanthanum nitrate hexahydrate and 2.6 g of nickel sulfate, and 2.2 g of maleic acid and 2.8 g of malonic acid as heteroelement-containing organic compounds are dissolved in 200 mL of water. did. The molar ratio of metal ions in the second metal aqueous solution is lanthanum: nickel = 1: 1.

d) 25 g of the lithium composite metal oxide was dispersed in 400 mL of pure water, and acetic acid was further added to prepare a first dispersion having a pH of 9. Further, water was added to 30 g of sodium hydroxide to prepare a basic aqueous solution of 100 mL.

e) Under stirring conditions at 1500 rpm, a first metal aqueous solution was added to the first dispersion to prepare a first mixed dispersion. Further, by adding a basic aqueous solution to the first mixed dispersion to precipitate zirconium hydride, an intermediate precursor containing zirconium hydride as a main component was attached to the surface of the lithium composite metal oxide. The pH of the first mixed dispersion at this time was 12.

The lithium composite metal oxide having the intermediate precursor adhered to the surface was separated by filtration and washing with water.

f) A lithium composite metal oxide having an intermediate precursor on the surface was dispersed in 400 mL of water, and acetic acid was further added to adjust the pH to 9.5 to prepare a second dispersion.

g) Under stirring conditions at 1500 rpm, a second metal aqueous solution was added to the second dispersion over about 2 hours to prepare a second mixed dispersion. In parallel with the addition of the second metal aqueous solution, the basic aqueous solution was added to the second mixed dispersion so that the pH of the second mixed dispersion was maintained at 9.5. By these operations, lanthanum hydroxide and nickel hydroxide are precipitated at the same time, and a conductive oxide precursor containing a composite metal hydroxide containing lanthanum hydroxide and nickel hydroxide as a main component is formed on the surface of the intermediate precursor. Adhered.

The lithium composite metal oxide to which the intermediate part precursor and the conductive oxide precursor were attached was separated by filtration and drying at 120 ° C. for 5 hours.

h) The separated lithium composite metal oxide was heated at 700 ° C. for 4 hours in an air atmosphere to obtain a material in which an intermediate portion and a conductive oxide portion were formed on the surface of the lithium composite metal oxide. The material of Example 1 was obtained by washing the material with water, filtering and drying.

In the material of Example 1, _{it is assumed that ZrO 2 is contained in the intermediate portion and LaNiO 3} is contained in the conductive oxide portion.

Next, the lithium ion secondary battery of Example 1 was manufactured as follows.

An aluminum foil having a thickness of 20 μm was prepared as a current collector for the positive electrode. 94 parts by mass of the material of Example 1 was mixed as the positive electrode active material, 3 parts by mass of acetylene black as the conductive auxiliary agent, and 3 parts by mass of polyvinylidene fluoride (PVDF) as the binder. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to prepare a slurry. The slurry was placed on the surface of the aluminum foil and applied using a doctor blade so that the slurry became a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove NMP by volatilization, and an active material layer was formed on the surface of the aluminum foil. The aluminum foil having the active material layer formed on the surface was compressed using a roll press machine, and the aluminum foil and the active material layer were firmly adhered to each other. The joint was heated at 120 ° C. for 6 hours in a vacuum dryer and cut into a predetermined shape (25 mm × 30 mm rectangular shape) to obtain a positive electrode.

The negative electrode was prepared as follows.

98.3 parts by mass of graphite was mixed with 1 part by mass of styrene-butadiene rubber and 0.7 parts by mass of carboxymethyl cellulose as a binder, and this mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry. This slurry is applied to a copper foil having a thickness of 20 μm, which is a current collector for negative electrodes, so as to form a film using a doctor blade, and the current collector to which the slurry is applied is dried and pressed, and the bonded product is pressed at 120 ° C. 6 It was heated in a vacuum dryer for an hour and cut into a predetermined shape (25 mm × 30 mm rectangular shape) to obtain a negative electrode.

A laminated lithium ion secondary battery was manufactured using the above positive and negative electrodes. Specifically, a rectangular sheet (27 × 32 mm, thickness 25 μm) made of a resin film having a three-layer structure of polypropylene / polyethylene / polypropylene was sandwiched between the positive electrode and the negative electrode as a separator to form a electrode plate group. This group of plates was covered with a set of two laminated films, the three sides were sealed, and then the electrolytic solution was injected into the bag-shaped laminated film. As the electrolytic solution, a solution prepared by dissolving _{LiPF 6} at a volume ratio of 3: 3: 4 in a solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate at a volume ratio of 3: 3: 4 was used. Then, by sealing the remaining one side, the laminated lithium ion secondary battery of Example 1 was obtained in which the four sides were hermetically sealed and the electrode plate group and the electrolytic solution were sealed. The positive electrode and the negative electrode are provided with tabs that can be electrically connected to the outside, and a part of the tabs extends to the outside of the lithium ion secondary battery of Example 1.

(Comparative Example 1)
As described below, the material of Comparative Example 1 having no intermediate portion was produced.

a) A lithium composite metal oxide represented by _{LiNi 5/10} Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

c) An aqueous metal solution prepared by dissolving 2.2 g of lanthanum nitrate hexahydrate and 1.3 g of nickel sulfate, and 1.1 g of maleic acid and 1.4 g of malonic acid as heteroelement-containing organic compounds in 100 mL of water. The molar ratio of metal ions in the metal aqueous solution is lanthanum: nickel = 1: 1.

d) 100 g of the lithium composite metal oxide was dispersed in 400 mL of pure water, and acetic acid was further added to prepare a dispersion having a pH of 3.5. Further, water was added to 30 g of sodium hydroxide to prepare a basic aqueous solution of 100 mL.

g) Under stirring conditions at 1500 rpm, a metal aqueous solution was added to the dispersion to prepare a mixed dispersion. Furthermore, by adding a basic aqueous solution to the mixed dispersion to precipitate lanthanum hydroxide and nickel hydroxide, the composite metal hydroxide of lanthanum hydroxide and nickel hydroxide is the main component on the surface of the lithium composite metal oxide. A conductive oxide precursor was attached. The pH of the mixed dispersion at this time was 12.

The lithium composite metal oxide to which the conductive oxide precursor was attached was separated by filtration and drying at 120 ° C. for 5 hours.

h) The separated lithium composite metal oxide was heated at 700 ° C. for 4 hours in an air atmosphere to obtain a material of Comparative Example 1 in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide.

Hereinafter, the lithium ion secondary battery of Comparative Example 1 was produced in the same manner as in Example 1 except that the material of Comparative Example 1 was used.

(Comparative Example 2)
h) The material of Comparative Example 2 was produced in the same manner as in Comparative Example 1 except that the heating temperature in the step was set to 600 ° C.

(Comparative Example 3)
Except for the use of the lithium composite metal oxide represented by _{LiNi 5/10} Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure as the positive electrode active material instead of the material of Example 1, the same as in Example 1. A lithium ion secondary battery of Comparative Example 3 was produced in the same manner.

(Evaluation example 1)
The surface of the lithium composite metal oxide having an intermediate precursor on the surface obtained in step e) of Example 1 and the material of Example 1 was observed with a scanning electron microscope (SEM). In addition, the surfaces of the materials of Comparative Example 1 and Comparative Example 2 were observed by SEM. Figures 1 to 4 show SEM images of each material.

From FIG. 1, it can be seen that the intermediate precursor is formed in the form of a film on the entire surface of the lithium composite metal oxide. Further, from FIG. 2, it can be seen that the conductive oxide portion having irregularities is formed on the surface of the material.

From FIGS. 3 and 4, it can be seen that the conductive oxide portion having irregularities is formed on the surface of the material. Comparing the SEM images of FIGS. 3 and 4, the material of Comparative Example 1 of FIG. 3 was observed in a darker color tone. This observation suggests that some of the metals constituting the lithium composite metal oxide have moved to the surface of the material of Comparative Example 1 due to the heat treatment at a higher temperature of 700 ° C.

On the other hand, the color tone of the SEM image of the material of Example 1 in FIG. 2 is similar to the color tone of the SEM image of the material of Comparative Example 2 of FIG. Therefore, in the material of Example 1, although the heat treatment was performed at 700 ° C., the presence of the intermediate portion suppressed a part of the metal constituting the lithium composite metal oxide from moving to the surface of the material. It can be said that it was done.

(Evaluation example 2)
As follows, the capacity retention rates of the lithium ion secondary batteries of Example 1 and Comparative Example 1 were measured.

For each lithium ion secondary battery (n = 2), 500 cycles of charge / discharge cycles in the voltage range of 4.24 V to 3.05 V were performed at 60 ° C. and 1 C rate. For example, 1C means a current value required to completely charge or discharge a battery in 1 hour at a constant current. The capacity retention rate (%) was calculated by the following formula. The results of the average value of n = 2 are shown in Table 2.
Capacity retention rate (%) = 100 x capacity after cycle / initial capacity

It can be said that the presence of the intermediate portion in the material of the present invention contributes to the optimization of the capacity retention rate of the lithium ion secondary battery. It was proved that the lithium ion secondary battery containing the material of the present invention as the positive electrode active material has an excellent capacity retention rate.

(Evaluation example 3)
The lithium ion secondary batteries of Example 1 and Comparative Example 3 were charged under the condition of 0 ° C. to a voltage of 4.24 V at a 0.5 C rate, paused for 60 seconds, and then 2. The charge / discharge cycle of discharging to 8 V and resting for 60 seconds was performed for 450 cycles. For each lithium ion secondary battery, the discharge resistance of each cycle at 4.24V and 2.8V was calculated based on the following formula.
(Discharge resistance at 4.24V) = (Voltage change amount at 4.24V during 60-second rest) / (0.5C current amount)
(Discharge resistance at 2.8V) = (Voltage change amount at 2.8V for 60 seconds) / (0.5C current amount)

Then, for each lithium ion secondary battery, the ratio of the discharge resistance at 450 cycles to the discharge resistance at the first cycle was calculated. The results are shown in Table 3.

Further, for each lithium ion secondary battery, the difference between the voltage after a 60-second pause at 4.24 V at 450 cycles and the voltage after a 60-second pause at 2.8 V at 450 cycles was calculated. The difference corresponds to the range of practical charge / discharge voltage of each lithium ion secondary battery at 450 cycles. The results are shown in Table 3.

From the result of the discharge resistance ratio at 4.24V, the lithium ion secondary battery of Example 1 has a higher rate of increase in discharge resistance at 4.24V after 450 cycles than the lithium ion secondary battery of Comparative Example 3. It turns out that is high. However, from the result of the discharge resistance ratio at 2.8 V, the lithium ion secondary battery of Example 1 had a discharge resistance at 2.8 V after 450 cycles as compared with the lithium ion secondary battery of Comparative Example 3. It can be seen that the rate of increase is low. Summarizing the results of the discharge resistance ratios at 4.24V and 2.8V, it can be said that the lithium ion secondary battery of Example 1 has a lower overall discharge resistance increase rate after 450 cycles.

Further, it can be seen that the lithium ion secondary battery of Example 1 has a wider range of practical charge / discharge voltage after 450 cycles than the lithium ion secondary battery of Comparative Example 3.

It can be said that the presence of the intermediate portion and the conductive oxide portion in the material of the present invention contributes to the suitability of the lithium ion secondary battery. It was confirmed that the lithium ion secondary battery containing the material of the present invention as the positive electrode active material is excellent.

(Reference manufacturing example 1)
a) A lithium composite metal oxide represented by _{LiNi 5/10} Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

b) 0.11 g of zirconium sulfate and 0.065 g of glycolic acid as a hydroxycarboxylic acid were dissolved in 40 mL of water to prepare a first metal aqueous solution. In the first metal aqueous solution, the molar ratio of zirconium to glycolic acid was 1: 2.

d) 25 g of the above-mentioned lithium composite metal oxide in powder form was dispersed in 400 mL of pure water, and further, sulfuric acid was added to prepare a first dispersion liquid adjusted to pH 10.

e) The first dispersion liquid and the first metal aqueous solution were mixed to obtain a first mixed dispersion liquid. Then, a sodium hydroxide solution was added over 1 hour until the pH of the first mixed dispersion was 12, to precipitate zirconium hydride on the surface of the lithium composite metal oxide. The lithium composite metal oxide in which zirconium hydride was precipitated on the surface was separated by filtration and dried at 120 ° C. for 5 hours.

The lithium composite metal oxide in which zirconium hydride was precipitated on the surface after drying was heated at 700 ° C. for 3 hours in an air atmosphere to obtain the lithium composite metal oxide of Reference Production Example 1 having an intermediate portion on the surface.

(Evaluation example 4)
The surface of the lithium composite metal oxide of Reference Production Example 1 was observed by SEM. FIG. 5 shows an SEM image of the lithium composite metal oxide of Reference Production Example 1. From the SEM image of FIG. 5, it can be said that the surface of the lithium composite metal oxide of Reference Production Example 1 is uniformly coated with the zirconium-containing film.

Claims (4)

Lithium composite metal oxide part and
On the surface of the lithium composite metal oxide portion, an intermediate portion made of ZrO ₂ and an intermediate portion
Wherein the surface of the intermediate portion, and organic conductive oxide unit containing LaNiO ₃ is a metal oxide, a method of manufacturing a material,
a) general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, Ge, Zn, Ru, Sc, A step of preparing a lithium composite metal oxide represented by at least one element selected from Sn, In, Y, Bi, S, Si, Na, K, P and V, 1.7 ≦ f ≦ 3).
b) A step of preparing a first metal aqueous solution containing Zr, which is a raw material for the intermediate portion.
c) A step of preparing a second metal aqueous solution containing La, which is a raw material for the conductive oxide portion.
d) A step of preparing a first dispersion liquid in which the lithium composite metal oxide is dispersed in water.
e) A step of mixing the first dispersion liquid and the first metal aqueous solution to obtain an alkaline first mixed dispersion liquid, and adhering an intermediate precursor to the surface of the lithium composite metal oxide.
f) The step of preparing a second dispersion liquid in which the lithium composite metal oxide having the intermediate precursor on the surface is dispersed in water, or the step of heating the lithium composite metal oxide having the intermediate precursor on the surface. A step of preparing a second dispersion liquid in which a lithium composite metal oxide having an intermediate portion on the surface is dispersed in water.
g) A step of mixing the second dispersion liquid and the second metal aqueous solution to obtain an alkaline second mixed dispersion liquid, and adhering a conductive oxide precursor to the intermediate portion precursor or the surface of the intermediate portion.
h) The step of heating the lithium composite metal oxide that has undergone the g) step,
Have a,
A method for producing a material, wherein the first metal aqueous solution and / or the second metal aqueous solution contains a hetero element-containing organic compound. Lithium composite metal oxide part and
On the surface of the lithium composite metal oxide portion, an intermediate portion made of ZrO ₂ and an intermediate portion
A method for producing a material, which comprises a _{conductive oxide portion containing LaNiO 3} which is a metal oxide on the surface of the intermediate portion.
a) general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 <c ≦ 3 / 10,0 ≦ e <1, D is W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, Rh, Zr, Fe, At least one element selected from Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, and a lithium composite metal represented by 1.7 ≦ f ≦ 3). The process of preparing the oxide,
b) A step of preparing a first metal aqueous solution containing Zr, which is a raw material for the intermediate portion.
c) A step of preparing a second metal aqueous solution containing La, which is a raw material for the conductive oxide portion.
d) A step of preparing a first dispersion liquid in which the lithium composite metal oxide is dispersed in water.
e) A step of mixing the first dispersion liquid and the first metal aqueous solution to obtain an alkaline first mixed dispersion liquid, and adhering an intermediate precursor to the surface of the lithium composite metal oxide.
f) The step of preparing a second dispersion liquid in which the lithium composite metal oxide having the intermediate precursor on the surface is dispersed in water, or the step of heating the lithium composite metal oxide having the intermediate precursor on the surface. A step of preparing a second dispersion liquid in which a lithium composite metal oxide having an intermediate portion on the surface is dispersed in water.
g) A step of mixing the second dispersion liquid and the second metal aqueous solution to obtain an alkaline second mixed dispersion liquid, and adhering a conductive oxide precursor to the intermediate portion precursor or the surface of the intermediate portion.
h) The step of heating the lithium composite metal oxide that has undergone the g) step,
Have a,
A method for producing a material, wherein the first metal aqueous solution and / or the second metal aqueous solution contains a hetero element-containing organic compound. The method for producing a material according to claim 1 or 2 , wherein the hetero element-containing organic compound is a chelate compound. A step of producing a positive electrode active material layer using the material produced by the production method according to any one of claims 1 to 3.
A method for manufacturing a lithium ion secondary battery having.

Images