JP6413949B2 - Material containing lithium composite metal oxide part and conductive oxide part - Google Patents

Description

  The present invention relates to a material containing a lithium composite metal oxide portion and a conductive oxide portion.

It is known that various materials are used as an active material of a lithium ion secondary battery. Among them, a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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 At least one element selected from 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 lithium ion secondary batteries.

  In recent years, researches based on the above lithium composite metal oxides have been actively conducted in order to provide better active materials.

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

JP 2012-018827 A JP 2012-256435 A

  However, the demand for the active material of the lithium ion secondary battery is increasing, and there is a strong desire to provide a new lithium composite metal oxide that can be a better active material.

  This invention is made | formed in view of this situation, and it aims at providing the new material which can become an active material, and its manufacturing method.

  As a result of intensive studies by the present inventor, the inventors succeeded in forming a conductive oxide portion on the surface of a lithium composite metal oxide by a specific manufacturing 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, and has completed the present invention.

The material of the present invention has a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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, V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3) And a conductive oxide part formed on the surface of the lithium composite metal oxide part.

  The present invention can provide a new material that can be an active material.

2 is a SEM image of the material of Example 1. 2 is a SEM image of the material of Example 2. 6 is a SEM image of the material of Example 4. 10 is a SEM image of the material of Example 8. 10 is a SEM image of the material of Example 10. 2 is a SEM image of the material of Comparative Example 1. 6 is a cross-sectional TEM image of the material of Example 4. 10 is a cross-sectional TEM image of the material of Example 9.

  The best mode for carrying out the present invention will be described below. Unless otherwise specified, the numerical range “x to y” described in this specification includes the lower limit x and the upper limit y. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

The material of the present invention has a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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, V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3) And a conductive oxide part formed on the surface of the lithium composite metal oxide part.

The method for producing the material of the present invention includes
a) General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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, Preparing a lithium composite metal oxide represented by at least one element selected from Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f ≦ 3),
b) a step of preparing a metal aqueous solution as a raw material of the conductive oxide part c) a step of preparing a dispersion in which the lithium composite metal oxide is dispersed in water;
d) mixing the dispersion and the aqueous metal solution to form a mixed dispersion, and attaching a conductive oxide precursor to the surface of the lithium composite metal oxide;
e) a step of heating the lithium composite metal oxide that has undergone the step d);
It is characterized by including.

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

First, a) process is demonstrated. a) Step is a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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, at least one element selected from Si, Na, K, P, and V, and a lithium composite metal oxide represented by 1.7 ≦ f ≦ 3) It is a process.

General formula: Li _a Ni _b Co _c Mn _{d De} 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 those satisfying the above conditions Although there is no limitation, it is preferable that 0 <b <1, 0 <c <1, 0 <d <1, and at least one of b, c, d is 10/100 <b <90/100. 10/100 <c <90/100, preferably 5/100 <d <70/100, <B <80/100, 12/100 <c <80/100, 10/100 <d <60/100 are more preferable, and 15/100 <b <70/100, 15/100 <c. More preferably, the ranges are <70/100, 12/100 <d <50/100.

  a, e, f may be any numerical value within the range defined by the general formula, and 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 the precursor thereof at 750 ° C. or higher, and the arrangement of the elements constituting the lithium composite metal oxide exhibits a layered rock salt structure by such firing. .

  For example, when lithium carbonate, nickel sulfate, manganese sulfate, and cobalt sulfate are used, the lithium composite metal oxide can be produced as follows (coprecipitation method). A sulfuric acid aqueous solution containing nickel sulfate, cobalt sulfate and manganese sulfate in predetermined amounts is made alkaline to obtain a coprecipitation slurry, which is dried to obtain a nickel cobalt manganese composite hydroxide. A predetermined amount of lithium carbonate is mixed with nickel cobalt manganese composite hydroxide and baked at 750 ° C. or higher to obtain a lithium composite metal oxide having a layered rock salt structure. The firing may be a multi-stage method in which firing is performed at a plurality of temperature conditions.

  The lithium composite metal oxide may be appropriately pulverized to be powdered, and further classified to a desired particle size. As 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 more preferably 1 μm or more, as measured 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 a solid phase method or spray dry method for a mixed raw material comprising a lithium raw material containing Li and a metal raw material containing one or more selected from Ni, Mn, and Co. It can be produced using a known method such as a hydrothermal method or a molten salt method.

  The solid phase method is a method in which a mixed raw material powder is mixed and / or pulverized, dried and / or molded as necessary, and then heated and fired to obtain a lithium composite metal oxide. The usual solid phase method is performed by mixing the raw materials at a ratio corresponding 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 shorter.

  The spray drying method is a method in which powder of a mixed raw material is dissolved in a liquid to form a solution, the solution is sprayed into the air to form mist, and the mist solution is heated. You may perform additional heating with respect to the powder obtained by the spray-drying method. The heating temperature in the spray drying method is preferably 500 ° C. or more and 1000 ° C. or less, and the heating time is preferably 3 hours or more and 8 hours or less.

  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 from 120 ° C. to 200 ° C., and the heating time is preferably from 2 hours to 24 hours.

  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 the molten liquid. The molar ratio of Li of the lithium composite metal oxide to be manufactured (Li of the lithium composite metal oxide to be manufactured / Li of the lithium compound) to Li of the lithium compound to be used 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. In preparing the lithium composite metal oxide within the range of 0 <e <1 in the above general formula, the doping element-containing compound may be added at any stage of producing the lithium composite metal oxide. . What is necessary is just to determine the compounding quantity of a dope element containing compound suitably so that it may become a desired dope amount.

  Next, step b) will be described. Step b) is a step of preparing a metal aqueous solution that is a raw material for the conductive oxide portion.

  In the production method of the present invention, a conductive oxide precursor is attached to the surface of the lithium composite metal oxide in step d). Here, the conductive oxide precursor is mainly composed of a metal hydroxide. More specifically, in the step d), a metal hydroxide having low solubility is precipitated mainly by pH control, and a phenomenon in which the metal hydroxide adheres to the surface of the lithium composite metal oxide occurs.

  Therefore, the metal aqueous solution in the step b) needs to contain a metal hydroxide that is hardly soluble in water or a metal hydroxide that can be hardly soluble in water at a specific pH. Examples of such metal ions include all metals other than alkali metals. In general, metals other than alkali metals are likely to exist in a solution state as metal ions in an acidic aqueous solution, and are likely to precipitate as metal hydroxides in a strong alkaline aqueous solution.

  One type of metal ion may be contained in the metal aqueous solution, or a plurality of types of metal ions may be contained. Although there is no restriction | limiting in particular in the density | concentration of metal aqueous solution, The metal aqueous solution which contains about 0.001-0.01 mol of metal ions with respect to 1 mol of lithium composite metal oxide to be used is suitable. Note that the metal aqueous solution may contain an alkali metal.

  In step b), one type of aqueous metal solution may be prepared, or a plurality of aqueous metal solutions containing different metal ions may be prepared.

  As a reference, the solubility products of typical metal hydroxides are listed in Table 1. It can be said that these metal hydroxides are hardly soluble in water.

  In order to prepare an aqueous metal solution, a metal salt containing a desired metal may be dissolved in water. Examples of the metal salt include sulfate, carbonate, nitrate, acetate, phosphate, halide, and hydrates thereof. If the solubility of the metal salt in water is low, an acid may be added.

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

  The aqueous metal 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 hetero element-containing organic compounds include amino groups, amide groups, imide groups, imino groups, cyano groups, azo groups, hydroxyl groups, alkoxy groups, carboxyl groups, ester groups, ether groups, carbonyl groups, which can be coordinated to metal ions, Phosphoric 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, phosphinic acid group, phosphinic acid ester group, thiol group, Examples 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, the hetero element-containing organic compound is preferably a chelate compound having a plurality of the above groups and capable of coordinating to a metal ion at a plurality of locations.

  Specific examples of chelate compounds include polyamine compounds such as ethylenediamine and diethylenetriamine, glycine, alanine, cysteine, glutamine, arginine, asparagine, aspartic acid, serine, ethylenediaminetetraacetic acid and other amino acids, malonic acid, succinic acid, glutaric acid, maleic acid. Acids, dicarboxylic acids such as phthalic acid, glycolic acid, lactic acid, tartronic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucine And hydroxycarboxylic acids such as acid, mevalonic acid, pantoic acid, quinic acid, shikimic acid, salicylic acid, gentisic acid, orthoric acid, mandelic acid, benzylic acid, 2-hydroxy-2-phenylpropionic acid .

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

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

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

  Usually, a dispersion in which lithium composite metal oxide is dispersed in water is extremely strong alkaline. Therefore, in step d), when the aqueous metal solution prepared in step b) is dropped into the extremely strong alkaline dispersion prepared in step c) to form a mixed dispersion, the metal ions contained in the aqueous metal solution are immediately removed. It is deposited as a metal hydroxide. Even in this case, a conductive oxide precursor mainly composed of a metal hydroxide can adhere to the surface of the lithium composite metal oxide, but precipitation of the metal hydroxide can occur throughout the mixed dispersion. When there is a large amount of metal hydroxide that does not adhere to the surface of the lithium composite metal oxide, and when the conductive oxide precursor adheres unevenly to the surface of the lithium composite metal oxide There is.

  Therefore, the pH of the dispersion in step c) is preferably adjusted by adding an acid. As the acid to be added, a weak acid is preferable from the viewpoint that significant fluctuations in pH can be suppressed by a buffering action. Examples of the weak acid include acetic acid, formic acid, oxalic acid, phosphoric acid, carbonic acid, and boric acid. Examples of suitable pH of the dispersion include 3 to 4 and 8 to 11.

  In the case of a dispersion having a pH of 3 to 4, in the step d), even if the dispersion and the metal aqueous solution prepared in the step b) are mixed, the metal hydroxide is not immediately precipitated. Therefore, the conductive oxide precursor can be uniformly attached to the surface of the lithium composite metal oxide by appropriately controlling the pH in the step d).

  In the case of a dispersion having a pH of 8 to 11, in the step d), when the dispersion and the metal aqueous solution prepared in the step b) are mixed, the surface of the lithium composite metal oxide is used as a deposition start site or a nucleus generation site. The conductive oxide precursor tends to be deposited in an orderly manner. Therefore, the crystallinity of the conductive oxide part obtained through the step e) is increased, and the powder resistance of the obtained material of the present invention is reduced.

  Next, step d) will be described. Step d) is a step in which the dispersion and the aqueous metal solution are mixed to form a mixed dispersion, and the conductive oxide precursor is attached to the surface of the lithium composite metal oxide. In step d), a metal hydroxide having low solubility is deposited on the surface of the lithium composite metal oxide mainly by pH control. The pH of the mixed dispersion is preferably 8 or more, and 8 to 11 can be exemplified as a preferable pH range. When a metal aqueous solution containing a hetero element-containing organic compound is used, the pH of the mixed dispersion is preferably 12 or more, more preferably 13 or more. In addition, the pH value of the mixed dispersion liquid in the step d) means a numerical value itself obtained by measuring the mixed dispersion liquid with a pH meter.

  If the pH of the dispersion is originally 8 or more, in step d), a basic aqueous solution is added to the mixed dispersion so that the pH of the mixed dispersion does not become less than 8 by adding an acidic metal aqueous solution. It is preferable to adjust the pH. In the case of a dispersion having a pH of 8 to 11, in step d), a basic aqueous solution may be added in addition to the addition of the acidic metal aqueous solution so as to maintain the pH of the mixed dispersion at 8 to 11. .

  In addition, as described in step c), in the case of a dispersion having a pH of 3 to 4, by appropriately performing pH control in step d), the conductive oxide precursor on the surface of the lithium composite metal oxide can be obtained. Adhesion can be performed uniformly. In particular, when mixing a dispersion of pH 3 to 4 and an aqueous metal solution of pH 4 to 6 containing a hetero element-containing organic compound, the basic aqueous solution is added at an appropriate rate, so that the metallic water in step d) is added. Oxide deposition can be slow and orderly. Therefore, in the material of the present invention, the adhesion between the lithium composite metal oxide portion and the conductive oxide portion can be increased, and the crystal orientations of both can be matched. As a result, the powder resistance of the material of the present invention is reduced.

  In order to mix the dispersion and the aqueous metal solution to obtain a mixed dispersion, it is preferable to add the aqueous metal solution to the dispersion. When the dispersion is extremely strong alkaline and when the pH of the dispersion is 8 to 11, the addition rate of the aqueous metal solution should be slow. A preferable addition rate of the metal aqueous solution is 10 to 1000 mL / h, a more preferable addition rate is 20 to 500 mL / h, and a more preferable addition rate is 50 to 300 mL / h.

  When there are a plurality of aqueous metal solutions prepared in step b), the plurality of aqueous metal solutions may be added to the dispersion at the same time, or may be added separately. When adding a plurality of metal aqueous solutions separately, one metal aqueous solution is added to the dispersion to form a mixed dispersion, and after attaching the conductive oxide precursor to the surface of the lithium composite metal oxide, By adding another metal aqueous solution, the conductive oxide precursor can be formed into a layer. That is, a plurality of conductive oxide precursor layers can be formed by repeating step d). In this case, a filtration step and a washing step may be performed for each step d).

  d) A basic aqueous solution is used for pH control in the step. The pH of the basic aqueous solution is preferably within the range of 9-14, more preferably within the range of 10-14, and even more preferably within the range of 11-14. The basic aqueous solution is prepared by dissolving a basic compound in water. The basic compound that can be used is not particularly limited as long as it dissolves in water and exhibits basicity. For example, alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, List alkali metal carbonates such as lithium carbonate, alkali metal phosphates such as trisodium phosphate, tripotassium phosphate and trilithium phosphate, alkali metal acetates such as sodium acetate, potassium acetate and lithium acetate, and ammonia Can do. A basic compound may be used independently and may use multiple together.

  When a metal hydroxide is precipitated by adding a basic aqueous solution to the mixed dispersion, the addition rate of the basic aqueous solution is preferably slow. A preferred basic aqueous solution addition rate is 10 to 1000 mL / h, a more preferred addition rate is 20 to 500 mL / h, and a more preferred addition rate is 50 to 300 mL / h.

  Step d) is preferably performed under stirring conditions. Furthermore, the mixed dispersion liquid may be cooled or superheated for the purpose of promoting the precipitation of the metal hydroxide.

  The lithium composite metal oxide having the conductive oxide precursor attached to the surface is separated, for example, through a filtration step, a washing step, and / or a drying step. As temperature of a drying process, 80-200 degreeC is preferable, 90-140 degreeC is more preferable, and 100-130 degreeC is further more preferable. The drying step may be omitted because it can be combined with the heating in step e).

  Next, step e) will be described. Step e) is a step of heating the lithium composite metal oxide that has passed through step d), and is a step of chemically synthesizing the material of the present invention. Specifically, this is a step in which a conductive oxide precursor mainly composed of a metal hydroxide is dehydrated to become a conductive oxide.

  As heating temperature, 500 degreeC or more is preferable, the inside of the range of 500-1000 degreeC is more preferable, and the inside of the range of 500-800 degreeC is more preferable. From the viewpoint of reducing the powder resistance of the material of the present invention, the heating temperature is preferably in the range of 700 to 900 ° C, more preferably in the range of 750 to 850 ° C. From the viewpoint that the discharge resistance of the secondary battery comprising the material of the present invention can be reduced, the heating temperature is preferably in the range of 500 to 800 ° C, more preferably in the range of 550 to 700 ° C. Moreover, also from a viewpoint that the capacity | capacitance maintenance factor of the secondary battery which comprises the material of this invention can be made suitable, the heating temperature is within the range of 500-800 degreeC, and the inside of the range of 550-700 degreeC is more preferable.

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

  e) The process is performed under atmospheric conditions.

  e) Through the process, the material of the present invention is formed. Moreover, it is preferable that the material of the present invention has a certain particle size distribution through a pulverization step and / or a classification step. As the range of the particle size distribution, the average particle diameter (D50) is preferably 100 μm or less, more preferably 1 μm or more and 50 μm or less, and even more preferably 1 μm or more and 30 μm or less in the measurement with a general laser scattering diffraction particle size distribution analyzer. 2 μm or more and 20 μm or less is particularly preferable.

The material of the present invention has a general formula of a layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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, V, and a lithium composite metal oxide portion represented by 1.7 ≦ f ≦ 3) And a conductive oxide portion formed on the surface of the lithium composite metal oxide portion.

  The conductive oxide portion means a portion that contains a metal oxide and has higher conductivity than the lithium composite metal oxide portion. Therefore, since the material of the present invention has higher conductivity than the lithium composite metal oxide itself, the powder resistance is low.

The metal oxide contained in the conductive oxide portion means an oxide containing a metal contained in the metal aqueous solution prepared in step b). For example, when the metal contained in the aqueous metal solution prepared in step b) is La, the metal oxide contained in the conductive oxide portion corresponds to La oxide such as La ₂ O _3, but part of La Is replaced with the metal constituting the lithium composite metal oxide part La, the metal constituting the lithium composite metal oxide part is introduced as a doped metal, such as La and La, or the oxygen or oxygen is insufficient or excessive from the theoretical amount In addition, an oxide in which La enters a lithium composite metal oxide, and a lithium composite metal oxide in which La and a metal constituting the lithium composite metal oxide are substituted are also included. That is, the assumed metal oxide contained in the conductive oxide portion is an oxide of all the valences that can be taken by the metal contained in the aqueous metal solution prepared in step b), and one of the metal of the oxide. Part is replaced with the metal constituting the lithium composite metal oxide part, the oxide in which the metal constituting the lithium composite metal oxide part has penetrated as a doped metal, and the metal or oxygen with respect to these oxides Is an oxide that is deficient or excessive than the theoretical amount, and further, an oxide in which the metal contained in the aqueous metal solution prepared in step b) penetrates into the lithium composite metal oxide, and the metal constituting the lithium composite metal oxide b) It is a lithium composite metal oxide substituted with a metal contained in the aqueous metal solution prepared in the process.

Specific examples of the metal oxide include, for example, 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 , (Sr, La) TiO ₃ , LaTiO 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, SrM _{O 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 , LiNiO ₃ can be exemplified.

  The metal oxide preferably has a perovskite crystal structure or the like.

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 excellent in thermal stability. For example, LaSr _x Co _y O ₃ (x + y = 1) is superior in thermal stability to LaNiO ₃ and thus can be said to be a preferred metal oxide.

  In general, since the lithium composite metal oxide portion having a layered rock salt structure has low conductivity, the specific metal oxide has higher conductivity than the lithium composite metal oxide portion.

  The conductive oxide part is preferably formed on the entire surface of the lithium composite metal oxide part. Further, the conductive oxide portion may be formed in a film shape on the entire surface of the lithium composite metal oxide portion, or may be formed in a state in which crystals protrude.

  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. In addition, when the range of the major axis L of the crystal of the conductive oxide portion in a state protruding from the surface of the material is exemplified, 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 of 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 that include the material of the present invention as a positive electrode active material. In the material of the present invention, a conductive oxide portion is formed on the surface of the lithium composite metal oxide portion. Due to the presence of the conductive oxide portion, it is considered that in the positive electrode having the material of the present invention as the positive electrode active material, it is possible to suppress the elution of the transition metal constituting the lithium composite metal oxide from the positive electrode to some extent.

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

  The current collector refers to a chemically inert electronic conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, 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, etc. Metal materials can be exemplified. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

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

  The positive electrode active material layer includes a positive electrode active material and, if necessary, a conductive additive and / or a binder.

  The positive electrode active material only needs to include the material of the present invention, and only the material of the present invention may be employed, or the material of the present invention and a known positive electrode active material may be used in combination.

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

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

  The binder plays a role of securing an active material or a conductive auxiliary agent to the surface of the current collector and maintaining a conductive network in the electrode. Examples of the binder include fluorine-containing resins 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, poly ( Examples thereof include acrylic resins such as (meth) acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose. These binders may be used singly or in plural.

  The blending ratio of the binder in the active material layer is preferably a mass ratio of active material: binder = 1: 0.001 to 1: 0.3, and 1: 0.005 to 1: 0. .2 is more preferable, and 1: 0.01 to 1: 0.15 is still more preferable. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when 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 bound to the surface of the current collector. What is necessary is just to employ | adopt suitably what was demonstrated with the positive electrode about a collector. The negative electrode active material layer includes a negative electrode active material and, if necessary, a conductive additive and / or a binder.

  Examples of the negative electrode active material include a carbon-based material capable of inserting and extracting lithium, an element that can be alloyed with lithium, a compound having an element that can be alloyed with lithium, a polymer material, and the like.

  Examples of the carbon-based material include non-graphitizable carbon, graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.

  Specifically, 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, 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 , 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 2 or LiSnO, particularly SiO _x (0.3 ≦ x ≦ 1.6, or 0.5 ≦ x ≦ 1.5) Is preferred.

  Among these, the negative electrode active material preferably includes a Si-based material having Si. The Si-based material may be made of silicon or / and a silicon compound capable of occluding / releasing lithium ions, for example, SiOx (0.5 ≦ x ≦ 1.5). Although silicon has a large theoretical charge / discharge capacity, silicon has a large volume change during charge / discharge. Therefore, the volume change of silicon can be mitigated by using SiOx containing silicon as the negative electrode active material.

The Si-based material preferably has a Si phase and a SiO ₂ phase. The Si phase is composed of simple silicon, and is a phase that can occlude and release Li ions, and expands and contracts as Li ions are occluded and released. The SiO ₂ phase is made 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 covered with the SiO ₂ phase is preferable. Furthermore, it is preferable that a plurality of micronized Si phases are covered with a 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 there is a possibility that a crack may occur in the negative electrode active material layer containing the Si-based material. On the other hand, if the mass ratio is too large, the amount of occlusion and release of Li ions of the negative electrode active material decreases, and the electric capacity per unit negative electrode mass of the battery decreases.

  Moreover, tin compounds, such as a tin alloy (Cu-Sn alloy, Co-Sn alloy, etc.), can be illustrated as a compound which has an element which can be alloyed with lithium.

  Specific examples of the polymer material include polyacetylene and polypyrrole.

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

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

  About the conductive support agent and binder used for a negative electrode, what was demonstrated in the positive electrode should just be employ | adopted suitably suitably with the same mixture ratio.

  In order to form an active material layer on the surface of the current collector, a current collecting 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 can be used. An active material may be applied to the surface of the body. Specifically, an active material, a solvent, and, if necessary, a binder and / or a conductive aid 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. In order to increase the electrode density, the dried product may be compressed.

  The electrolytic solution includes a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent.

  As the non-aqueous solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of 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 part or all of hydrogen in the chemical structure of the specific solvent is substituted with fluorine may be employed.

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 an electrolytic solution, 0.5 mol / L to 1.7 mol of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 in} a nonaqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate. 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 while preventing a short circuit due to contact between the two electrodes. As separators, natural resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polymer), polyester, polyacrylonitrile, and other polysaccharides, cellulose, amylose and other polysaccharides, fibroin, keratin, lignin, suberin, etc. Examples thereof include porous bodies, nonwoven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. The separator may have a multilayer structure.

  Next, the manufacturing method of a lithium ion secondary battery is demonstrated.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting 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 that communicate with the outside using a lead for current collection, etc., an electrolyte is added to the electrode body and a lithium ion secondary Use batteries. Moreover, the lithium ion secondary battery of this invention should just be charged / discharged in the voltage range suitable for the kind of active material contained in an electrode.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape 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 a 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. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples.

Example 1
The material of Example 1 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A metal aqueous solution in which 1.3 g of nickel nitrate hexahydrate and 1.7 g of glycine as a heteroelement-containing organic compound were dissolved in 100 mL of water was prepared.

  c) 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 pH 9 dispersion. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. Further, by adding the basic aqueous solution to the mixed dispersion to precipitate nickel hydroxide, the conductive oxide precursor mainly composed of nickel hydroxide was adhered to the surface of the lithium composite metal oxide. The pH of the mixed dispersion at this time was 12.

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

  e) The separated lithium composite metal oxide was heated at 700 ° C. for 4 hours in an air atmosphere to obtain a material in which a conductive oxide portion was 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.

(Example 2)
The material of Example 2 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A metal aqueous solution in which 2.2 g of lanthanum nitrate hexahydrate and 2.8 g of ethylenediaminetetraacetic acid as a heteroelement-containing organic compound were dissolved in 100 mL of water was prepared.

  c) 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 pH 9 dispersion. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. Further, the basic aqueous solution was added to the mixed dispersion to precipitate lanthanum hydroxide, thereby attaching a conductive oxide precursor mainly composed of lanthanum hydroxide to the surface of the lithium composite metal oxide. The pH of the mixed dispersion at this time was 13 or more.

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

  e) The separated lithium composite metal oxide was heated at 700 ° C. for 4 hours in an air atmosphere to obtain a material in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide. The material of Example 2 was obtained by washing the material with water, filtering and drying.

(Example 3)
The material of Example 3 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A metal aqueous solution in which 2.2 g of lanthanum nitrate hexahydrate, 0.3 g of strontium carbonate, and 0.85 g of cobalt sulfate were dissolved in 100 mL of water was prepared. The molar ratio of metal ions in the aqueous metal solution is lanthanum: strontium: cobalt = 1: 0.4: 0.6.

  c) 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. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. Further, by adding the above basic aqueous solution to the mixed dispersion to precipitate lanthanum hydroxide, strontium hydroxide and cobalt hydroxide, lanthanum hydroxide, strontium hydroxide and cobalt hydroxide are deposited on the surface of the lithium composite metal oxide. A conductive oxide precursor mainly composed of a composite metal hydroxide containing was deposited. The pH of the mixed dispersion at this time was 12.

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

  e) The separated lithium composite metal oxide was heated at 800 ° C. for 4 hours in an air atmosphere to obtain a material in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide. The material of Example 3 was obtained by washing the material with water, filtering and drying.

Example 4
The material of Example 4 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A metal aqueous solution in which 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 a heteroelement-containing organic compound were dissolved in 100 mL of water was prepared. The molar ratio of metal ions in the aqueous metal solution is lanthanum: nickel = 1: 1.

  c) 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. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. Further, by adding the above 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 mainly formed on the surface of the lithium composite metal oxide. A conductive oxide precursor as a component was deposited. The pH of the mixed dispersion at this time was 12.

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

  e) The separated lithium composite metal oxide was heated at 600 ° C. for 4 hours in an air atmosphere to obtain a material of Example 4 in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide.

  Next, the lithium ion secondary battery of Example 4 was manufactured as follows.

  An aluminum foil having a thickness of 20 μm was prepared as a positive electrode current collector. 94 parts by mass of the material of Example 4 as a positive electrode active material, 3 parts by mass of acetylene black as a conductive additive, and 3 parts by mass of polyvinylidene fluoride (PVDF) as a binder were mixed. 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, thereby removing NMP by volatilization and forming an active material layer 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 bonded. The joined product was heated at 120 ° C. for 6 hours with a vacuum dryer, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and used as a positive electrode.

  The negative electrode was produced as follows.

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

A laminate type lithium ion secondary battery was manufactured using the positive electrode and the negative electrode. 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 to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ in a solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 3: 3: 4 so as to be 1 mol / L was used. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery of Example 4 in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. The positive electrode and the negative electrode have a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the lithium ion secondary battery of Example 4.

(Example 5)
e) The material of Example 5 was produced in the same manner as in Example 4 except that the heating temperature in the step was 700 ° C.

(Example 6)
e) The material and lithium ion secondary battery of Example 6 were manufactured in the same manner as in Example 4 except that the heating temperature in the step was 800 ° C.

(Example 7)
e) The material of Example 7 was produced in the same manner as in Example 4 except that the heating temperature in the step was 900 ° C.

(Example 8)
The material of Example 8 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A metal aqueous solution in which 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 a heteroelement-containing organic compound were dissolved in 100 mL of water was prepared. The molar ratio of metal ions in the aqueous metal solution is lanthanum: nickel = 1: 1.

  c) 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 9.5. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. In parallel with the addition of the aqueous metal solution, the basic aqueous solution was added to the mixed dispersion so that the pH of the mixed dispersion was maintained at 9.5. By these operations, lanthanum hydroxide and nickel hydroxide are simultaneously precipitated, and a conductive oxide precursor mainly composed of a composite metal hydroxide containing lanthanum hydroxide and nickel hydroxide on the surface of the lithium composite metal oxide. Attached.

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

  e) The separated lithium composite metal oxide was heated at 600 ° C. for 4 hours in an air atmosphere to obtain a material of Example 8 in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide.

Example 9
The material of Example 9 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) 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 a hetero element-containing organic compound were dissolved in 100 mL of water, and further an aqueous sodium hydroxide solution Was added to prepare an aqueous metal solution having a pH of 5. The molar ratio of metal ions in the aqueous metal solution is lanthanum: nickel = 1: 1.

  c) 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. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) An aqueous metal solution was added to the dispersion under stirring conditions at 1500 rpm to prepare a mixed dispersion. Simultaneously with the addition of the aqueous metal solution, the basic aqueous solution was added until the pH of the mixed dispersion reached 10. By conducting these operations, lanthanum hydroxide and nickel hydroxide are precipitated at a slow rate, so that the surface of the lithium composite metal oxide is electrically conductive mainly composed of a composite metal hydroxide containing lanthanum hydroxide and nickel hydroxide. A functional oxide precursor was deposited.

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

  e) The separated lithium composite metal oxide was heated at 600 ° C. for 4 hours in an air atmosphere to obtain a material in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide. The material of Example 9 was obtained by washing the material with water, filtering, and drying.

(Example 10)
The material of Example 10 was manufactured as follows.

a) A lithium mixed metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ having a layered rock salt structure was prepared.

  b) A first metal aqueous solution was prepared by dissolving 2.2 g of lanthanum nitrate hexahydrate and 2.8 g of ethylenediaminetetraacetic acid as a heteroelement-containing organic compound in 100 mL of water. Also, a second metal aqueous solution was prepared by dissolving 1.3 g of nickel sulfate and 1.7 g of glycine as a hetero element-containing organic compound in 100 mL of water.

  c) 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 first dispersion having a pH of 9. Moreover, the basic aqueous solution which added water to 30 g of sodium hydroxide and made it 100 mL was prepared.

  d) A first metal dispersion was added to the first dispersion under stirring conditions at 1500 rpm to prepare a first mixed dispersion. Further, by adding the basic aqueous solution to the first mixed dispersion to precipitate lanthanum hydroxide, the first conductive oxide precursor mainly composed of lanthanum hydroxide is formed on the surface of the lithium composite metal oxide. Attached. The pH of the first mixed dispersion at this time was 13.

  Filtration and water washing were performed to separate the lithium composite metal oxide to which the first conductive oxide precursor was attached. Subsequently, the 2nd dispersion liquid which disperse | distributed the lithium composite metal oxide to which the 1st electroconductive oxide precursor was made to adhere in 400 mL of pure waters was prepared.

  Under stirring conditions at 1500 rpm, the second metal aqueous solution was added to the second dispersion to prepare a second mixed dispersion. Further, nickel hydroxide is mainly deposited on the surface of the lithium composite metal oxide to which the first conductive oxide precursor is adhered by adding the basic aqueous solution to the second mixed dispersion to precipitate nickel hydroxide. A second conductive oxide precursor as a component was deposited. The pH of the second mixed dispersion at this time was 13.

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

  e) The separated lithium composite metal oxide was heated at 600 ° C. for 4 hours in an air atmosphere to obtain a material in which a conductive oxide portion was formed on the surface of the lithium composite metal oxide. The material of Example 10 was obtained by washing the material with water, filtering, and drying.

  A lithium ion secondary battery of Example 10 was produced in the same manner as in Example 4 except that the material of Example 10 was used as the positive electrode active material.

(Comparative Example 1)
The lithium composite metal oxide represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ was used as the material of Comparative Example 1. A lithium ion secondary battery of Comparative Example 1 was produced in the same manner as in Example 4 except that the material of Comparative Example 1 was used as the positive electrode active material.

Table 2 shows a list of materials of Examples 1 to 10. In addition, the conductive oxide assumed in Table 2 includes a lithium composite metal oxide in which a part of the metal constituting the conductive oxide is represented by LiNi _5/10 Co _3/10 Mn _2/10 O ₂ Also included are oxides substituted with a metal constituting the above.

(Evaluation example 1)
About the material of Examples 1-9 and the material of the comparative example 1, it used for the powder resistivity measuring system (Mitsubishi Analytech Co., Ltd.), and measured the volume resistivity of the powder. The results are shown in Table 3.

  It can be seen that the volume resistivity of the material is reduced due to the presence of the conductive oxide portion. Moreover, from the viewpoint that the powder resistance of the material of the present invention can be reduced from the results of the volume resistivity of the materials of Examples 4 to 7 in which only the heating temperature in step e) is changed, the heating temperature is 700. Within the range of -900 degreeC is preferable and it can be said that the inside of the range of 750-850 degreeC is more preferable.

  Further, from comparison between Example 4, Example 8, and Example 9, it can be seen that the volume resistivity of the material is changed by adjusting the pH of the aqueous metal solution, the dispersion, and the mixed dispersion.

(Evaluation example 2)
The surface of the materials of Examples 1, 2, 4, 8, and 10 and the material of Comparative Example 1 were observed with a scanning electron microscope (SEM). 1 to 6 show SEM images of the respective materials. 1-6, it can confirm that the conductive oxide part is formed in the surface of the material of each Example.

  From the SEM image of the material of Example 8 shown in FIG. 4, a polyhedral conductive oxide portion having a major axis of about 40 nm was observed on the surface of the material of Example 8. The crystallinity of the conductive oxide portion of the material of Example 8 is presumed to be high, and the high crystallinity of the conductive oxide portion is thought to have led to the low volume resistivity of Evaluation Example 1. .

  In addition, as shown in FIG. 5, it can be said that the material of Example 10 has many film-like conductive oxide portions that uniformly cover the lithium composite metal oxide.

(Evaluation example 3)
About the material of Example 4 and Example 9, a cross section was formed by Ar ion milling using an ion slicer (EM-09100IS, manufactured by JEOL Ltd.), and the cross section was observed with a transmission electron microscope (TEM). did. FIG. 7 shows a cross-sectional TEM image of the material of Example 4, and FIG. 8 shows a cross-sectional TEM image of the material of Example 9.

  In the TEM image of FIG. 7, the upper part including the horizontal line near the center corresponds to the lithium composite metal oxide part, and the lower part of the horizontal line near the center and the unclear part is the conductive oxide part. Applicable. In FIG. 7, there is a portion where a gap is observed between the lithium composite metal oxide portion and the conductive oxide portion, and the lithium composite metal oxide portion has an orderly conductive oxidation. Bonding of object parts was not observed. The thickness of the conductive oxide portion was about 150 nm.

  In the TEM image of FIG. 8, the right portion including the vertical line near the center corresponds to the lithium composite metal oxide portion, and the left portion of the vertical line near the center is a slightly unclear portion of the conductive oxide. Corresponds to the division. In FIG. 8, it is observed that the lithium composite metal oxide portion and the conductive oxide portion are bonded while maintaining a crystallographic orientation relationship. The thickness of the conductive oxide portion was about 10 nm. The adhesion of the conductive oxide part of the material of Example 9 to the lithium composite metal oxide part is presumed to be high, and the high adhesion led to the low volume resistivity of Evaluation Example 1. Conceivable. Note that the TEM image in FIG. 8 has a magnification about 10 times higher than the TEM image in FIG.

(Evaluation example 4)
About the lithium ion secondary battery of Example 4, Example 6, and Comparative Example 1, discharge resistance was measured with the following method. Each lithium ion secondary battery was adjusted to a potential difference of 3.05 V and discharged at a 2.5 C rate for 10 seconds. The discharge resistance (Ω) was determined by the following formula. The results are shown in Table 4.
Discharge resistance (Ω) = | Voltage before discharge−Voltage after discharge | / Current value

  It can be seen that the discharge resistance of the lithium ion secondary battery is reduced due to the presence of the conductive oxide portion. Moreover, it turns out that the discharge resistance of a lithium ion secondary battery changes with the heating temperature in the process e).

(Evaluation example 5)
The capacity maintenance rates of the lithium ion secondary batteries of Example 4, Example 6, and Comparative Example 1 were measured as follows.

First, each lithium ion secondary battery was charged to 25 ° C., 0.33 C rate, voltage 4.5 V, and the discharge capacity was measured when discharged to a voltage 3.0 V at 0.33 C rate. This was the initial capacity. Further, each lithium ion secondary battery was subjected to 100 charge / discharge cycles in the range of voltage 4.5V to 3.0V at 60 ° C. and 1C rate, and then left at room temperature for 5 hours or more, and then the initial capacity measurement The discharge capacity was measured under the same conditions. This was the post-cycle capacity. For example, 1C means a current value required to fully charge or discharge the battery in one hour at a constant current. The capacity retention rate (%) was obtained by the following formula.
Capacity maintenance ratio (%) = 100 × capacity after cycle / initial capacity

  The results are shown in Table 5.

  It was confirmed that the secondary battery comprising the material of the present invention as the positive electrode active material has an excellent capacity retention rate. Moreover, it turns out that the capacity | capacitance maintenance factor of a lithium ion secondary battery changes with the heating temperature in the process e).

(Evaluation example 6)
For the lithium ion secondary batteries of Example 4 and Example 10, the initial discharge resistance was measured by the following method. Each lithium ion secondary battery was adjusted to a potential difference of 3.1 V and discharged at a 2.5 C rate for 10 seconds. The initial discharge resistance (Ω) was determined by the following formula.
Initial discharge resistance (Ω) = | Voltage before discharge−Voltage after discharge | / Current value

  Each lithium ion secondary battery is charged at a constant current up to 4.5 V at 25 ° C. and a 0.33 C rate, held at 4.5 V for 5 hours, and then discharged at a constant current up to 2.5 V. Then, 30 charging / discharging cycles of holding 2.5 V for 5 hours were performed, and after standing at room temperature for 5 hours or longer, the discharge resistance after the charging / discharging cycle was measured by the same method as described above. The results are shown in Table 6.

  The material of Example 4 is obtained by attaching a conductive oxide precursor using a mixed metal aqueous solution containing both La and Ni in step d). On the other hand, the material of Example 10 is obtained by sequentially attaching each conductive oxide precursor using a metal aqueous solution containing La and a metal aqueous solution containing Ni in step d).

  When there are a plurality of metal aqueous solutions in step b), the material of the present invention obtained by performing step d) for each metal aqueous solution is more suitable when used as a positive electrode active material of a lithium ion secondary battery. It can be said that it exhibits excellent characteristics.

Claims (16)

a) General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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 , Fe , Ge, Zn, Ru, Sc, Sn, A step of preparing a lithium composite metal oxide represented by at least one element selected from In, Y, Bi, S, Si, Na, K, P, and V, 1.7 ≦ f ≦ 3),
b) a step of preparing a metal aqueous solution as a raw material of the conductive oxide part c) a step of preparing a dispersion in which the lithium composite metal oxide is dispersed in water;
d) mixing the dispersion and the aqueous metal solution to form a mixed dispersion, and attaching a conductive oxide precursor to the surface of the lithium composite metal oxide;
e) a step of heating the lithium composite metal oxide that has undergone the step d);
A method for producing a material in which a conductive oxide portion is formed on the surface of the lithium composite metal oxide, comprising :
The conductive oxide portion is present on the outermost surface of the material,
In the conductive oxide part, CaVO ₃ , MnO ₂ , La ₂ CuO ₄ , La ₂ NiO ₄ , SnO ₂ , Tl ₂ Mn ₂ O ₇ , Fe ₂ O ₃ , CaMnO ₃ , SrMnO 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 , VO, V ₂ O ₃ , LaMnO ₃ , CaCrO ₃ , LaCoO ₃ , (ZnO) ₅ , SrCrO ₃ , In _0.97 Y _0.03 O ₃ , 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 _{u 2 O 7, SrRuO 3,} CaRuO 3, CrO 2, MoO 2, ReO 2, LaNiO 3, SrVO 3, ReO 3, IrO 2, RuO 2, RhO 2, OsO 2, NbO, NiO, LaSr x Co y O ₃ (x + y = 1), a metal oxide selected from NaCoO ₃ , NaNiO ₃ , LiCoO ₃ , and LiNiO ₃ is contained . a) General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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 , Fe , Ge, Zn, Ru, Sc, Sn, A step of preparing a lithium composite metal oxide represented by at least one element selected from In, Y, Bi, S, Si, Na, K, P, and V, 1.7 ≦ f ≦ 3),
b) a step of preparing a metal aqueous solution as a raw material of the conductive oxide part c) a step of preparing a dispersion in which the lithium composite metal oxide is dispersed in water;
d) mixing the dispersion and the aqueous metal solution to form a mixed dispersion, and attaching a conductive oxide precursor to the surface of the lithium composite metal oxide;
e) a step of heating the lithium composite metal oxide that has undergone the step d);
A method for producing a material in which a conductive oxide portion is formed on the surface of the lithium composite metal oxide, comprising :
The manufacturing method in which the step b) is a step of preparing a metal aqueous solution by dissolving a metal salt which is a raw material of the conductive oxide part and a hetero element-containing organic compound which is a substance different from the metal salt in water. . a) General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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 , Fe , Ge, Zn, Ru, Sc, Sn, A step of preparing a lithium composite metal oxide represented by at least one element selected from In, Y, Bi, S, Si, Na, K, P, and V, 1.7 ≦ f ≦ 3),
b) a step of preparing a metal aqueous solution as a raw material of the conductive oxide part c) a step of preparing a dispersion in which the lithium composite metal oxide is dispersed in water;
d) mixing the dispersion and the aqueous metal solution to form a mixed dispersion, and attaching a conductive oxide precursor to the surface of the lithium composite metal oxide;
e) a step of heating the lithium composite metal oxide that has undergone the step d);
A method for producing a material in which a conductive oxide portion is formed on the surface of the lithium composite metal oxide, comprising :
The manufacturing method which makes pH of the dispersion liquid of the said c) process in the range of 3-4 . The manufacturing method of Claim 1 or 3 in which the said metal aqueous solution contains a hetero element containing organic compound. The method according to claim 2 or 4 , wherein the hetero element-containing organic compound is a chelate compound. The process according to any one of claims 1 to 5, 8 or more pH of the mixed dispersion. The manufacturing method of Claim 1 or 2 which makes pH of the dispersion liquid of a process c in the range of 3-4. The production method according to claim 1 or 2 , wherein the pH of the dispersion in the step c) is in the range of 8-11. The production method according to claim 8 , wherein the pH of the mixed dispersion is maintained within a range of 8 to 11. The production method according to any one of claims 1 to 9 , wherein the pH of the aqueous metal solution in step b) is in the range of 4 to 6. b) a metal aqueous solution in step a plurality of method according to any one of claims 1 to 10 for the d) step for each aqueous metal solution. The manufacturing method according to any one of claims 1 to 11 , wherein the heating temperature in step e) is 500 to 800 ° C. A step of producing the material by the production method according to claim 1,
  Producing a positive electrode comprising the material as a positive electrode active material;
The manufacturing method of the positive electrode which has this. A step of producing the positive electrode by the production method according to claim 13;
  Producing a lithium ion secondary battery comprising the positive electrode;
The manufacturing method of the lithium ion secondary battery which has this. General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} 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 , Fe , Ge, Zn, Ru, Sc, Sn, In, A lithium composite metal oxide portion represented by at least one element selected from Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f ≦ 3);
A conductive oxide portion formed on the surface of the lithium composite metal oxide portion;
A material to have a,
The conductive oxide portion is present on the outermost surface of the material,
In the conductive oxide part, CaVO ₃ , MnO ₂ , La ₂ CuO ₄ , La ₂ NiO ₄ , SnO ₂ , Tl ₂ Mn ₂ O ₇ , Fe ₂ O ₃ , CaMnO ₃ , SrMnO 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 , VO, V ₂ O ₃ , LaMnO ₃ , CaCrO ₃ , LaCoO ₃ , (ZnO) ₅ , SrCrO ₃ , In _0.97 Y _0.03 O ₃ , 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 _{u 2 O 7, SrRuO 3,} CaRuO 3, CrO 2, MoO 2, ReO 2, LaNiO 3, SrVO 3, ReO 3, IrO 2, RuO 2, RhO 2, OsO 2, NbO, NiO, LaSr x Co y O ₃ (x + y = 1), a material containing a metal oxide selected from NaCoO ₃ , NaNiO ₃ , LiCoO ₃ , and LiNiO ₃ . A lithium ion secondary battery comprising the material according to claim 15 .