JP2015215951A - Active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel active material which exhibits a satisfactory capacity-keeping rate.SOLUTION: An active material comprises: a first composition part expressed by the general formula, LiaNibCocMndDeOf(where 0.2≤a1≤1.5, b1+c1+d1+e1=1, 0≤e1<1, D is at least one element selected from Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf and Rf, 1.7≤f1≤2.1); and a second composition part expressed by the general formula, LiNiCoMnDO(where 0.2≤a2≤1.5, b2+c2+d2+e2=1, 0≤e2<1, D is at least one element selected from Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf and Rf, 1.7≤f2≤2.1, provided that at least one of the relations of c2<c1 and d2>d1 holds). The first and second composition parts are delocalized.

Description

  The present invention relates to an active material, a method for producing the same, and a lithium ion secondary battery including the active material.

The active material of the nonaqueous electrolyte 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 ≦ 1.5, b + c + d + e = 1, 0 ≦ e <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, The lithium composite metal oxide represented by at least one element selected from V, Mo, Nb, W, La, Hf, and Rf, 1.7 ≦ f ≦ 2.1) is an active material for a lithium ion secondary battery. As a general purpose.

  However, when the lithium composite metal oxide represented by the above general formula is used as an active material of a high-capacity secondary battery driven at a high voltage required for an in-vehicle secondary battery, for example, Due to the lack of resistance to high voltage, the capacity maintenance rate of the secondary battery could not be maintained at a satisfactory level.

For this reason, in recent years, various studies for improving the resistance to high voltages of various materials used as active materials have been conducted. In this examination, the following three methods are generally proposed.
1) Doping the active material with a different element 2) Forming a protective film on the active material surface 3) Changing the composition of the active material surface layer

  The method and effect of the above 1) will be specifically described. By doping the active material with an element that did not exist in the active material such as Al or Zr, the active material deteriorates due to charge / discharge, that is, absorption / release of Li. Can be suppressed.

  When the method and effect of 2) are specifically described, as disclosed in Patent Document 1 below, a protective film is formed on the surface of the active material with a phosphate to prevent direct contact between the electrolyte and the active material. Thus, it is possible to suppress deterioration of the active material mainly due to contact with the electrolytic solution.

  The above method 3) will be described in detail. Patent Document 2 below discloses an active material having an increased Al composition on the surface layer, obtained by coating the surface of the active material with an Al compound and heat-treating it. Has been. Moreover, the following patent document 3 and the following patent document 4 disclose an active material in which core particles are coated with a coating portion having a higher cobalt concentration and a lower manganese concentration than the core particles.

JP 2006-127932 A JP 2001-196063 A JP2013-182882A JP 2013-182783 A

  As described above, new active materials are provided one after another.

  The present invention has been made in view of such circumstances, and even when used in a secondary battery driven at a high voltage, it maintains a good Li storage capacity, that is, a good capacity maintenance rate. The purpose is to provide new active materials to be shown.

General formula of layered rock salt structure: Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1.5, b + c + d + e = 1, 0 ≦ e1 <1, D is Fe, Cr, Cu, Zn, At least one element selected from Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, and Rf, 1.7 ≦ f It is known that the active material represented by ≦ 2.1) expands and contracts with charge / discharge of the secondary battery, that is, with desorption and adsorption of lithium from the active material. More specifically, the c-axis of the layered rock salt structure expands as lithium is desorbed from the active material. This phenomenon is considered to be caused by the following mechanism. When lithium ions are desorbed from the layered rock salt structure, a plurality of negatively charged oxygens coordinated to lithium are adjacent to each other. Since these oxygens are electrically repelled, the c-axis expands as a result. The expansion of the c-axis is considered to be deeply related to the deterioration of the active material. In order to facilitate understanding, a schematic diagram of a layered rock salt structure is shown in FIG.

Here, the present inventors have for the LiNi _b Co _c Mn _d O ₂ representing the general formula perform first-principles calculation, investigate nickel, the relationship between the size of the expansion of the cobalt and the composition ratio of manganese to the c-axis did.

  As a result, it was found that the expansion of the c-axis is suppressed as the cobalt ratio is decreased, and is suppressed as the manganese ratio is increased.

  However, since manganese is inactive during the charge / discharge reaction, simply using an active material having a small cobalt ratio and a large manganese ratio results in a reduction in the capacity of the active material.

  Here, the present inventor has conceived a new lithium composite metal oxide in which a first composition part that is highly active during charge and discharge and a second composition part that has a relatively small c-axis expansion during charge and discharge are mixed. .

That is, the active material of the present invention has a general formula: Li _a1 Ni _b1 Co _c1 Mn _d1 D _e1 O _f1 (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr At least one element selected from Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf, 1.7 ≦ f1 ≦ 2.1) and a general formula: Li _a2 Ni _b2 Co _c2 Mn _{d2 De2O f2} (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, At least one element selected from Hf and Rf, 1.7 ≦ f2 ≦ 2.1 However, at least one of c2 <c1 or d2> d1 is satisfied), and the first composition part and the second composition part are delocalized. It is characterized by that.

  Since the first composition part and the second composition part are delocalized, the expansion occurring in the first composition part is buffered in the second composition part, or the stress concentration of the expansion is relieved, and as a result, the active material It is thought that the overall deterioration is alleviated.

  Since deterioration of the active material of the present invention is suppressed, a secondary battery including the active material exhibits a good capacity maintenance rate.

It is a schematic diagram of a layered rock salt structure. 5 is a scatter diagram showing the relationship between the Co content ratio c and Δc for the results in Table 1. FIG. 5 is a scatter diagram showing the relationship between the Mn content ratio d and Δc for the results in Table 1. FIG. d) It is a schematic diagram of a process. e) It is a schematic diagram of a process. It is a HAADF-STEM image of the active material of the present invention. It is the figure which superimposed the HAADF-STEM image of the active material of this invention, and the elemental map of Co and Mn obtained by STEM-EDX. It is the figure which superimposed the HAADF-STEM image of the active material of this invention, and the element map of Co and Mn obtained by STEM-EDX, and also divided each composition part with the continuous line. It is a LAADF-STEM image of the active material of the present invention. It is a BF-STEM image of the active material of the present invention. It is an ABF-STEM image of the interface location of the 2nd composition part and the 1st composition part of the active material of the present invention. It is an ABF-STEM image of the 1st composition part of the active material of the present invention.

  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 active material of the present invention has a general formula: Li _a1 Ni _b1 Co _c1 Mn _d1 D _e1 O _f1 (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr, Cu Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf, at least one element; 7 ≦ f1 ≦ 2.1) and a general formula: Li _a2 Ni _b2 Co _c2 Mn _{d2 De2O f2} (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, At least one element selected from Rf, 1.7 ≦ f2 ≦ 2.1, but small At least c2 <c1 or d2> d1), wherein the first composition part and the second composition part are non-localized. It is characterized by becoming.

The active material of the present invention has a general formula: Lia ₁ Nib ₁ Coc ₁ Mnd ₁ De ₁ Of ₁ (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr At least one element selected from Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf, 1.7 ≦ f1 ≦ 2.1) and a general formula: Li _a2 Ni _b2 Co _c2 Mn _{d2 De2O f2} (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, At least one element selected from Hf and Rf, 1.7 ≦ f2 ≦ 2.1, However, at least one of c2 <c1 or d2> d1 is satisfied), and the first composition part and the second composition part have a single crystal structure. The active material primary particle | grains as are formed.

  Here, the single crystal structure means that the crystal structures of the first composition part and the second composition part are substantially the same, and the crystal orientations of both are continuous in substantially the same direction. Although they are adjacent to each other and have a partially different composition, they are as if they were in a single crystal state.

  The active material of the present invention is a combined body in which a large number of particles composed of primary particles of the active material and the other first composition part and / or second composition part are combined. The shape of the active material primary particles is not particularly limited, but many flat particles are observed. When the active material of the present invention is observed with a microscope, the major axis length of the active material primary particles is approximately in the range of 100 to 1200 nm, and the minor axis length of the active material primary particles is approximately in the range of 100 to 500 nm. It is. The “major axis length of the active material primary particles” means the length of the longest portion of the active material primary particles when the active material primary particles are observed. The “short diameter length of the active material primary particles” means the length of the longest portion in the orthogonal direction of the long diameter in the active material primary particles when the active material primary particles are observed.

  The shape of the active material of the present invention is not particularly limited. When a preferable average particle diameter (D50) of the active material when measured with a general laser scattering diffraction type particle size distribution analyzer is given, it is preferably 100 μm or less, more preferably 1 μm or more and 50 μm or less, further preferably 1 μm or more and 30 μm or less. 2 μm or more and 20 μm or less is particularly preferable. When the average particle size is less than 1 μm, there may be a problem that, when an electrode is produced using an active material, the adhesion with the current collector is easily impaired. If the average particle diameter exceeds 100 μm, the size of the electrode may be affected, or the separator constituting the secondary battery may be damaged.

  Furthermore, a preferable active material of the present invention is such that the first composition part and the second composition part are delocalized, and the first composition part and the second composition part are a single crystal structure. Active material primary particles are formed.

General formula concerning the first composition part: Li _a1 Ni _b1 Co _c1 Mn _d1 D _e1 O _f1 (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf, at least one element, 1.7 ≦ f1 ≦ 2.1), the values of b1, c1 and d1 are not particularly limited as long as the above conditions are satisfied, but 0 <b1 <1, 0 <c1 <1, 0 <d1 <1 And at least one of b1, c1, and d1 is in the range of 10/100 <b1 <90/100, 10/100 <c1 <90/100, 5/100 <d1 <70/100. Preferably, 12/100 <b1 <80 More preferably, the ranges are 100, 12/100 <c1 <80/100, 10/100 <d1 <60/100, 15/100 <b1 <70/100, 15/100 <c1 <70/100, More preferably, the range is 12/100 <d1 <50/100.

  About a1, e1, f1, what is necessary is just a numerical value within the range prescribed | regulated by a general formula, Preferably 0.5 <= a1 <= 1.3, 0 <e1 <0.2, 1.8 <= f1 <= 2.1 More preferably, 0.8 ≦ a1 ≦ 1.2, 0 <e1 <0.1, 1.9 ≦ f1 ≦ 2.05 can be exemplified.

General formula _concerning the second composition part: Li _a2 Ni _b2 Co _c2 Mn _{d2 De2} O _f2 (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf, at least one element, 1.7 ≦ f2 ≦ 2.1 (provided that at least one of c2 <c1 or d2> d1 is satisfied), the values of b2, c2 and d2 are not particularly limited as long as the above conditions are satisfied. <B2 <1, 0 <c2 <c1, d1 <d2 <1 are preferable, and both of c2 <c1 and d2> d1 may be satisfied. Moreover, it is preferable that at least one of b2, c2, and d2 is in the range of 0 <b2 <b1, 0 <c2 <c1, d1 <d2 <1, 10/100 <b2 <b1, 10/100 <. More preferably, the ranges are c2 <c1, d1 <d2 <90/100, 10/100 <b2 <90/100, 10/100 <c2 <c1- (5/100), d1 + (5/100). <D2 <90/100 is more preferable, and 12/100 <b2 <80/100, 10/100 <c2 <c1- (10/100), d1 + (10/100) <d2 <90 / A range of 100 is particularly preferred.

  The values a2, e2, and f2 may be numerical values within the range defined by the general formula, and preferably 0.5 ≦ a2 ≦ 1.3, 0 <e2 <0.2, 1.8 ≦ f2 ≦ 2.1. More preferably, 0.8 ≦ a2 ≦ 1.2, 0 <e2 <0.1, 1.9 ≦ f2 ≦ 2.05 can be exemplified.

Incidentally, the active material of the present invention generally formula layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 1.5, b + c + d + e = 1,0 ≦ e < 1, D is from Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf It can be expressed by at least one selected element, 1.7 ≦ f ≦ 2.1). The values of a, b, c, d, e, and f are the values of a1, b1, c1, d1, e1, and f1 of the first composition part of the mass of the first composition part relative to the total mass of the active material of the present invention. The sum of the value multiplied by the ratio and the value obtained by multiplying the value of the second composition part a2, b2, c2, d2, e2, f2 by the ratio of the mass of the second composition part to the total mass of the active material of the present invention. Is calculated by Preferred examples of b, c and d include 0 <b <1, 0 <c <1, and 0 <d <1, and more preferably 0 <b <80/100 and 0 <c <70/100. 10/100 <d <1, and 10/100 <b <70/100, 12/100 <c <60/100, 20/100 <d <70/100. The ranges of 25/100 <b <60/100, 15/100 <c <50/100, and 25/100 <d <60/100 are particularly preferable.

  Further, as will be apparent from Evaluation Example 2 described later, the active material of the present invention is more suitable due to the presence of the doping element represented by D in the above general formula. Therefore, examples of preferable ranges for e include 0 <e <0.2 and 0 <e <0.1.

  The mass ratio of the first composition part and the second composition part in the active material of the present invention is preferably in the range of 1:10 to 10: 1, and the preferred range is 1: 5 to 5: 1, 1: 3 to 3: 1, 2: 5 to 5: 2, 1: 2 to 2: 1, 3: 5 to 5: 3, 7:10 to 10: 7, 4: 5 to 5: 4, and 9: A range of 10 to 10: 9 is particularly preferable.

Here, for the active material represented by the layered rock salt structure LiNi _b Co _c Mn _d O ₂ , the present inventor has changed the amount of change Δc (c-axis lattice constant when 67% of Li is desorbed from the active material. Ii) was calculated using the first principle calculation under the following conditions. The results are shown in Table 1. Moreover, the scatter diagram which showed the relationship between Co content ratio c and (DELTA) c, and the scatter diagram which showed the relationship between Mn content ratio d and (DELTA) c are shown in FIG.2 and FIG.3, respectively.

Software: quantum espresso (PWscf)
Exchange correlation interaction: GGAPBE functional Calculation method: PAW (Project Augmented Wave) method Cut-off of wave function: 50 Ry

  FIG. 2 shows that the smaller the Co content ratio c of the active material, the smaller the tendency of Δc. FIG. 3 shows that the larger the Mn content ratio d of the active material, the smaller the Δc tends to be.

  The second composition part of the active material of the present invention has a smaller Co content ratio than the first composition part or a larger Mn content ratio than the first composition part. From the composition relationship between the first composition part and the second composition part and the first principle calculation result, it can be said that the second composition part has a smaller Δc than the first composition part. An active material having a smaller Δc has a smaller amount of crystal deformation of the active material during charge / discharge, so that deterioration during charge / discharge is suppressed. Therefore, it can be said that it has been theoretically confirmed that the second composition part is more stable during charge and discharge than the first composition part.

  In the active material of the present invention, since the first composition part and the second composition part are delocalized, the c-axis expansion generated in the first composition part is suppressed from being localized and excessive. In addition, since the c-axis expansion is buffered by the second composition part, it is considered that the deterioration of the entire active material is alleviated.

  Moreover, since the active material primary particle which consists of a 1st composition part and a 2nd composition part is a single crystal structure, the expansion which arises in a 1st composition part is directly buffered in a 2nd composition part, and the active material 1 Deterioration of secondary particles is suppressed. As a result, it is considered that the deterioration of the entire active material is preferably alleviated.

  The manufacturing method of the active material of this invention is demonstrated. There are two methods for producing the active material of the present invention.

  The first production method includes the following steps a) to f).

a) Step of preparing a first aqueous solution in which nickel salt, cobalt salt and manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b3: c3: d3 (b3 + c3 + d3 = 10) b) Nickel salt, cobalt A second aqueous solution in which a salt and a manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b4: c4: d4 (b4 + c4 + d4 = 10, but at least satisfies either c4 <c3 or d4> d3) C) a step of preparing a basic aqueous solution d) a step of supplying the first aqueous solution and the second aqueous solution simultaneously to the basic aqueous solution, and containing nickel, cobalt and manganese in a molar ratio b3: c3: d3. 1 primary particles and second primary particles containing nickel, cobalt and manganese in a molar ratio b4: c4: d4 are formed. Extent e) mixing said first primary particles and step f) the binding particles and lithium salts second primary particles to form bound particles bound to one another, firing the firing step

The second production method includes the following steps a) to c) and g) to l).
a) Step of preparing a first aqueous solution in which nickel salt, cobalt salt and manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b3: c3: d3 (b3 + c3 + d3 = 10) b) Nickel salt, cobalt A second aqueous solution in which a salt and a manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b4: c4: d4 (b4 + c4 + d4 = 10, but at least satisfies either c4 <c3 or d4> d3) C) Step of preparing a basic aqueous solution g) The first aqueous solution is supplied to the basic aqueous solution, and first primary particles containing nickel, cobalt and manganese in a molar ratio b3: c3: d3 are provided. Forming step h) heating the first primary particles to form a first dehydrated product i) supplying the second aqueous solution to the basic aqueous solution; J) a step of forming second primary particles containing ru, cobalt and manganese in a molar ratio of b4: c4: d4 j) a step of heating the second primary particles to form a second dehydrated k) particle composite In the apparatus, the first dehydrated product and the second dehydrated product are mixed to produce dehydrated bonded particles in which the first dehydrated product and the second dehydrated product are bonded to each other. L) The dehydrated bonded particles and lithium salt Firing process to mix and fire

  Here, a) the first aqueous solution in the step, d) the first primary particles in the step, g) the first primary particles in the step, and h) the first dehydrated product in the active material of the present invention. It is the basis for the composition of nickel, cobalt and manganese in one composition part. And b) 2nd aqueous solution of a process, d) 2nd primary particle of a process, i) 2nd primary particle of a process, j) 2nd dehydration of a process is the 2nd in the active material of the present invention. It is the basis for the composition of nickel, cobalt and manganese in the composition part. Therefore, the molar ratio of nickel, cobalt and manganese in the step a) or the step b) may be set in accordance with the molar ratio of nickel, cobalt and manganese in the first composition part or the second composition part.

  Further, the binder particles in step e) and the dehydrated binder particles in step k) are the basis of the active material primary particles of the present invention.

  Examples of the nickel salt used in the steps a) and b) include nickel sulfate, nickel carbonate, nickel nitrate, nickel acetate, and nickel chloride. Examples of the cobalt salt used in the step include cobalt sulfate, cobalt carbonate, cobalt nitrate, cobalt acetate, and cobalt chloride. Examples of the manganese salt used in this step include manganese sulfate, manganese carbonate, manganese nitrate, manganese acetate, and manganese chloride.

  A preferable metal concentration range of the first aqueous solution or the second aqueous solution is 0.01 to 4 mol / L, more preferably 0.05 to 3 mol / L, still more preferably 0.1 to 2 mol / L, particularly Preferably it is 0.5-1.5 mol / L. In the first production method, it is preferable that the first aqueous solution and the second aqueous solution have the same metal concentration because the primary particle formation rates in the step d) are approximately the same. Moreover, when the 1st aqueous solution or the 2nd aqueous solution considers that the metal contained in these aqueous solutions precipitates at a next process, the higher concentration is preferable.

  The pH of the basic aqueous solution in step c) is preferably 9 to 14, more preferably 10 to 13.5, and still more preferably 11 to 13. In addition, pH prescribed | regulated by this specification says the value at the time of measuring at 25 degreeC. The basic compound that can be used is not particularly limited as long as it dissolves in water and exhibits basicity, and examples thereof include alkali metal hydroxides such as ammonia, sodium hydroxide, potassium hydroxide, and lithium hydroxide, sodium carbonate, and carbonate. List alkali metal carbonates such as potassium and lithium carbonate, alkali metal phosphates such as trisodium phosphate, tripotassium phosphate and trilithium phosphate, and alkali metal acetates such as sodium acetate, potassium acetate and lithium acetate. Can do. A basic compound may be used independently and may use multiple together. In the aqueous solutions of steps d), e), g), and i), it is preferable to maintain the pH within a suitable range. Therefore, the basic aqueous solution of step c) has at least a buffer capacity. Preferably a basic compound is included. Examples of the basic compound having a buffering ability include ammonia, alkali metal carbonates, alkali metal phosphates, and alkali metal acetates.

  Step c) is preferably carried out in a reaction vessel equipped with a stirring device, and more preferably carried out in a reaction vessel equipped with a device capable of introducing an inert gas such as nitrogen or argon. Moreover, the reaction tank provided with the apparatus used as a constant temperature condition is more preferable. c) Specific examples of the steps are given below. Water is charged into a reaction vessel equipped with a stirrer, a nitrogen gas introducing device and a heating device, and heated to 40 ° C. Nitrogen gas is introduced into the reaction vessel to create a nitrogen gas atmosphere. An aqueous sodium hydroxide solution and aqueous ammonia are added to the reaction vessel to prepare a basic aqueous solution.

  Hereinafter, steps d) to f) of the first production method will be described.

  Step d) is a step in which the first aqueous solution and the second aqueous solution are simultaneously supplied to the basic aqueous solution from different locations to simultaneously form the first primary particles and the second primary particles, respectively. The first primary particles and the second primary particles are made of metal hydroxides contained in the first aqueous solution and the second aqueous solution, respectively. d) In the step, metal ion hydroxides contained in the first aqueous solution or the second aqueous solution are formed, each of these hydroxides forms a particle nucleus, and each primary particle of a certain size is formed. Form. Each primary particle is presumed to be in a single crystal state. The first primary particles and the second primary particles have a particle length of approximately 1000 nm or less when observed with a microscope, and the range is approximately 80 to 1000 nm. In the present specification, “particle length” means the length of the longest portion of each particle at the time of observation.

  d) A schematic diagram of the process is shown in FIG. As shown in FIG. 4, the first aqueous solution 1 and the second aqueous solution 2 are simultaneously supplied to the basic aqueous solution 3, respectively. And the metal ion contained in the 1st aqueous solution 1 becomes a hydroxide in the basic aqueous solution 3, the 1st particle nucleus 11 is formed, and the 1st primary particle 12 of a fixed magnitude | size is formed. . Similarly, metal ions contained in the second aqueous solution 2 become hydroxides in the basic aqueous solution 3 to form second particle nuclei 21, and second primary particles 22 having a certain size are formed. The

  Step d) is preferably performed under the same conditions as described in step c). The stirring speed and temperature conditions may be appropriately set within a range suitable for nucleation and primary particle formation. Preferable stirring speed can be 50 to 10,000 rpm, more preferably 100 to 3000 rpm, and still more preferably 200 to 1500 rpm. When the pH of the basic aqueous solution fluctuates with the supply of the first aqueous solution and the second aqueous solution, or when a basic compound such as ammonia is lost from the reaction tank due to vaporization, the basic compound employed in step c) is included. An aqueous solution may be appropriately supplied to maintain a pH and ammonia concentration suitable for nucleation and primary particle formation. From the viewpoint of process stability, the supply rate of the first aqueous solution and the supply rate of the second aqueous solution are preferably constant. A preferable supply rate is 1 to 30 mL / min. More preferably, 1.5 to 15 mL / min. More preferably, it is 2-8 mL / min. Can be mentioned.

  Step e) is a step of forming bonded particles in which the first primary particles and the second primary particles are bonded to each other. Specifically, it is a step of continuously holding and / or stirring while reducing the liquid in step d) as necessary. The step e) is preferably performed continuously with the step d). Furthermore, in step e), as in step d), a first aqueous solution, a second aqueous solution, and an aqueous solution containing a basic compound may be appropriately supplied. It may be difficult to strictly distinguish between the step e) and the step d). From the relationship of the solubility of each particle, it is preferable to carry out the step e) with a smaller amount of liquid than the step d). In step e), it is preferable to hold and / or stir the liquid until the desired size of the binding particles is obtained. The binding particles have a particle length of approximately 20 μm or less when observed with a microscope, and the particle length range is approximately 2 to 20 μm. The resulting bonded particles can be separated by filtration. The bound particles after separation may be subjected to step e) again as necessary. The bound particles after separation are preferably dehydrated under heating conditions. As heating conditions, 100-400 degreeC and 1 to 50 hours can be mentioned. In the step e), in addition to the bonded particles in which the first primary particles and the second primary particles are bonded to each other, the bonded particles in which the first primary particles or the second primary particles are bonded are also included. May be obtained. In some cases, a bonded particle in which a plurality of bonded particles are bonded is obtained.

  e) A schematic diagram of the process is shown in FIG. As shown in FIG. 5, the first primary particles 12 and the second primary particles 22 are bonded to each other by the collision of the first primary particles 12 and the second primary particles 22 by stirring. Particles 4 are formed.

  Step f) is a step in which the binding particles and lithium salt obtained in step e) are mixed and fired to obtain the active material of the present invention. Examples of the lithium salt include lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium oxalate, and lithium halide. What is necessary is just to determine suitably the compounding quantity of lithium salt so that it may become an active material of a desired lithium composition. As an example, in the entire raw material used in step f), the lithium salt so that the molar ratio of lithium to the sum of nickel, cobalt and manganese is in the range of 0.2: 1 to 1.2: 1. What is necessary is just to determine the compounding quantity of.

  Examples of the mixing device include a mortar and pestle, a stirring mixer, a V-type mixer, a W-type mixer, a ribbon-type mixer, a drum mixer, and a ball mill.

  What is necessary is just to set baking conditions suitably within the range of 500-1000 degreeC and 1 to 20 hours, for example. The firing temperature may be changed during firing, and firing may be performed at a plurality of temperatures. Examples of suitable firing conditions include primary firing under conditions of 600 to 800 ° C. and 8 to 12 hours, and then secondary firing under conditions of 800 to 1000 ° C. and 3 to 7 hours. it can. The active material obtained after calcination preferably has a constant particle size distribution through a pulverization step and 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. When the average particle size is less than 1 μm, there may be a problem that, when an electrode is produced using an active material, the adhesion with the current collector is easily impaired. If the average particle diameter exceeds 100 μm, the size of the electrode may be affected, or the separator constituting the secondary battery may be damaged.

  Hereinafter, steps g) to l) of the second production method will be described.

  Step g) is a step of forming the first primary particles by supplying the first aqueous solution to the basic aqueous solution. g) Each condition of a process may be the conditions which excluded the location about the 2nd aqueous solution and the 2nd primary particle from explanation of the above-mentioned d) process.

  Step h) is a step in which the first primary particles made of the metal hydroxide obtained in step g) are heated to form a first dehydrated product. As heating conditions, 100-400 degreeC and 1 to 50 hours can be mentioned, for example.

  Step i) is a step in which the second aqueous solution is supplied to the basic aqueous solution prepared in step c) to form second primary particles. i) Each condition of the process may be a condition excluding the part relating to the first aqueous solution and the first primary particles from the description of the above d) process.

  Step j) is a step in which the second primary particles made of the metal hydroxide obtained in step i) are heated to form a second dehydrated product. As heating conditions, 100-400 degreeC and 1 to 50 hours can be mentioned, for example.

  Step k) is a step of producing dehydrated bonded particles in which the first dehydrated product and the second dehydrated product are combined with each other in the particle compounding apparatus and the first dehydrated product and the second dehydrated product are bonded to each other. Examples of the particle composite apparatus include a hybridization system (NHS) and Miraro from Nara Machinery Co., Ltd., Mechano-Fusion and Nobilta from Hosokawa Micron Corporation, and a theta composer from Tokuju Works.

  Step l) is a step in which dehydrated bonded particles and a lithium salt are mixed and fired, and specific conditions are the same as those in step f).

  In addition, when it is desired to add the doping element represented by the general formula D to the active material of the present invention, any of the steps a) to e) and g) to k), or f) What is necessary is just to add a dope element containing compound in the time before baking. 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.

  The active material of the present invention is composed of a first composition part and a second composition part, and the first composition part and the second composition part are delocalized. And the active material of this invention can be recognized as a different thing from the conventional active material.

  The active material disclosed in Patent Document 3 will be described in detail according to its production method. First, the first sulfate aqueous solution is dropped into the carbonate ion-containing aqueous solution to form carbonate particles. Next, a second sulfate aqueous solution is dropped to attach the metal carbonate contained in the second sulfate aqueous solution around the carbonate particles to obtain two-layered carbonate particles. Then, the carbonate particles in the two-layer state and lithium carbonate are mixed, and the mixture is fired to obtain a lithium composite metal oxide having a core and a covering portion. That is, in the active material disclosed in Patent Document 3, the first composition part and the second composition part as referred to in the present invention are localized in the inside of the particle and the periphery of the particle, respectively.

  The active material disclosed in Patent Document 4 will be described in detail according to its production method. First, core particles are prepared, and then the surface of the core particles is coated with cobalt hydroxide to obtain two-layer coated particles. Next, two-layer coated particles and lithium carbonate are mixed, and the mixture is baked to obtain an active material having a core and a coating portion. That is, in the active material disclosed in Patent Document 4, as in the active material disclosed in Patent Document 3, the first composition portion and the second composition portion referred to in the present invention are localized in the inside of the particle and the periphery of the particle, respectively. It has become.

  In the present specification, “delocalization” means that the active material of the present invention is 1 in each of the first composition part and the second composition part like the active materials disclosed in Patent Document 3 and Patent Document 4 described above. It means that it is not an active material localized at a place.

  Further, a mixture obtained by simply mixing a lithium composite metal oxide and another lithium composite metal oxide is naturally not an active material of the present invention.

In view of these, the active material of the present invention has a general formula: Lia ₁ Nib ₁ Coc ₁ Mnd ₁ De ₁ Of ₁ (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is selected from Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf A first composition part represented by at least one element, 1.7 ≦ f1 ≦ 2.1), and a general formula: Li _a2 Ni _b2 Co _c2 Mn _{d2 De2O f2} (0.2 ≦ a2 ≦ 1.5) , B2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb , At least one element selected from W, La, Hf, and Rf; ≦ f2 ≦ 2.1 (provided that at least either c2 <c1 or d2> d1 is satisfied), and the active materials disclosed in Patent Documents 3 and 4 It can also be expressed as not.

  A lithium ion secondary battery can be manufactured using the active material of the present invention. The lithium ion secondary battery of this invention contains a negative electrode, a separator, and electrolyte solution in addition to the positive electrode which has the active material of this invention as a battery component.

  The positive electrode includes a current collector and an active material layer containing the active material of the present invention. Note that the active material layer may contain an active material other than the active material of the present invention.

  The current collector refers to a chemically inert electronic high 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, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer.

  The current collector can take the form of a foil, a sheet, a film, a line, a bar, and the like. Therefore, metal foils, such as copper foil, nickel foil, aluminum foil, stainless steel foil, can be used suitably as a collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 10 μm to 100 μm.

  A positive electrode can be obtained by forming an active material layer on the surface of the current collector.

  The active material layer may contain a conductive additive. The conductive assistant is added to increase the conductivity of the electrode. Examples of the conductive assistant include carbon black, graphite, acetylene black, ketjen black (registered trademark), and vapor grown carbon fiber (VGCF) which are carbonaceous fine particles. These conductive assistants can be added to the active material layer alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a conductive support agent, For example, it can be set as 1-50 mass parts or 1-30 mass parts with respect to 100 mass parts of active materials.

  The active material layer may contain a binder. The binder serves to bind the active material and the conductive additive to the surface of the current collector. 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, and alkoxysilyl group-containing resins. be able to. Although there is no restriction | limiting in particular about the usage-amount of a binder, For example, it can be set as 5-50 mass parts with respect to 100 mass parts of active materials.

  In order to form an active material layer on the surface of the current collector, the surface of the current collector can be formed using a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method. What is necessary is just to apply | coat an active material to. Specifically, an active material layer-forming composition containing an active material and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste, and then the collection is performed. After applying to the surface of the electric body, it is dried. If necessary, the dried product may be compressed to increase the electrode density.

  Examples of the solvent include N-methyl-2-pyrrolidone (NMP), methanol, and methyl isobutyl ketone (MIBK).

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

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

  The current collector, binder and conductive additive are the same as those described for the positive electrode.

  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, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black. 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 compounds having elements 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. When the mass ratio is less than 1, the expansion and contraction of the Si-based material increases, and the negative electrode active material layer containing the Si-based material may be cracked. On the other hand, when the mass ratio exceeds 3, 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.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. Examples of the separator include a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, or polyethylene, or a ceramic porous film.

  The electrolytic solution includes 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 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, methyl ethyl 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.

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 dimethyl carbonate. A solution dissolved at a concentration of about 1 / l can be exemplified.

  As a manufacturing method of a lithium ion secondary battery, what is necessary is just to have the process of arrange | positioning the positive electrode of this invention. Hereinafter, a specific method for producing a lithium ion secondary battery will be exemplified. A separator is sandwiched between the positive electrode and the negative electrode 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 between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal connected to the outside using a current collecting lead or the like, an electrolytic solution is added to the electrode body to form a lithium ion secondary battery. It is good to do.

  Since the active material of the present invention relaxes the expansion and contraction associated with the adsorption and desorption of lithium ions as a whole, the lithium ion secondary battery using the active material of the present invention is less likely to deteriorate even after repeated charge and discharge. A good capacity maintenance rate. As a result, the lithium ion secondary battery of the present invention can exhibit a good capacity retention rate even under high potential driving conditions. Here, the high potential driving condition means that the operating potential of lithium ions with respect to lithium metal is 4.3 V or higher, and further 4.4 V to 4.6 V or 4.5 V to 5.5 V. In the lithium ion secondary battery of the present invention, the charging potential of the positive electrode can be set to 4.3 V or higher, further 4.4 V to 4.6 V or 4.5 V to 5.5 V on the basis of lithium. Note that, under the driving conditions of a general lithium ion secondary battery, the operating potential of lithium ions with respect to lithium metal is less than 4.3V.

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

  The lithium ion secondary battery of the present invention can be mounted on a vehicle. Since the lithium ion secondary battery of the present invention maintains a large charge / discharge capacity and has excellent cycle performance, a vehicle equipped with the lithium ion secondary battery is a high-performance vehicle.

  The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, an electric forklift, an electric wheelchair, and an electric assist. Bicycles and electric motorcycles are examples.

  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. In the following, unless otherwise specified, “part” means part by mass, and “%” means mass%.

Example 1
Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water to prepare a first aqueous solution having a molar ratio of nickel, cobalt, and manganese of 6: 2: 2. The total concentration of nickel, cobalt and manganese in the first aqueous solution was 0.9 mol / L.

  Nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in water to prepare a second aqueous solution having a molar ratio of nickel, cobalt and manganese of 4: 2: 4. The total concentration of nickel, cobalt and manganese in the second aqueous solution was 0.9 mol / L.

  Water was put into a reaction vessel equipped with a stirrer and a nitrogen introduction tube, and heated to 40 ° C. with stirring. Nitrogen was continuously supplied from the nitrogen introduction tube, and the reaction vessel was maintained under a nitrogen atmosphere. A 16% by weight aqueous solution of sodium hydroxide and a 28% by weight aqueous solution of ammonia were supplied to the reaction vessel to prepare a basic aqueous solution having an ammonia concentration of 9 g / L and a pH of 11.6. In addition, as above-mentioned, pH prescribed | regulated by this specification is a value at the time of measuring at 25 degreeC.

  The first aqueous solution and the second aqueous solution were simultaneously supplied to the basic aqueous solution under stirring conditions at a speed of 1000 rpm. The supply rates of the first aqueous solution and the second aqueous solution were 0.4 mL / min. Met. In order to maintain the ammonia concentration of the basic aqueous solution at about 9 g / L and the pH of the basic aqueous solution at about 11.6 to 11.8, a 16 mass% aqueous solution of sodium hydroxide and an aqueous 3 mass% solution of ammonia were added to the reaction vessel. Were appropriately supplied. Then, first primary particles containing nickel, cobalt and manganese in a molar ratio of 6: 2: 2 and second primary particles containing nickel, cobalt and manganese in a molar ratio of 4: 2: 4 were formed.

  The amount of the aqueous solution in the reaction vessel is reduced, and stirring is continued while maintaining the ammonia concentration in the aqueous solution at about 9 g / L and the pH of the aqueous solution at about 11.2 to 11.3. Bonded particles in which primary particles were bonded to each other were formed. After the binding particles were filtered, the amount of the aqueous solution in the reaction vessel was reduced again, and the binding particles were added to the aqueous solution to grow the binding particles. The grown bonded particles were separated by filtration and washed with water. The washed bonded particles were heated at 300 ° C. for 20 hours for dehydration.

The dehydrated binding particles and lithium carbonate were mixed so that a molar ratio of lithium to the total of nickel, cobalt, and manganese was 1.1: 1 to obtain a mixture. 0.5% by mass of zirconium phosphate was added to the mixture and mixed. The obtained mixture was subjected to primary firing at 650 ° C. for 10 hours. Next, secondary firing was performed at 850 ° C. for 5 hours to obtain a fired product. The fired product was cooled, pulverized and classified to obtain a lithium composite metal oxide having an average particle size of 6 μm. This was used as the active material of Example 1. The active material of Example 1 is represented by an average composition of Li _1.13 Ni _{4.97 / 10} Co _{1.99 / 10} Mn _{2.98 / 10} Zr _{0.05 / 10} O ₂ .

(Example 2)
The active material of Example 2 was produced in the same manner as in Example 1 except that zirconium phosphate was not used.

(Example 3)
Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water to prepare a first aqueous solution having a molar ratio of nickel, cobalt, and manganese of 6: 2: 2. The total concentration of nickel, cobalt and manganese in the first aqueous solution was 0.9 mol / L.

  Water was put into a reaction vessel equipped with a stirrer and a nitrogen introduction tube, and heated to 40 ° C. with stirring. Nitrogen was continuously supplied from the nitrogen introduction tube, and the reaction vessel was maintained under a nitrogen atmosphere. Sodium hydroxide 16 mass% aqueous solution and ammonia 28 mass% aqueous solution were supplied to the reaction tank, and basic aqueous solution with ammonia concentration of 9 g / L and pH of 12.4 was prepared.

  Said 1st aqueous solution was supplied with respect to the basic aqueous solution made into stirring conditions with a speed | rate of 1000 rpm. The supply rate of the first aqueous solution was 0.4 mL / min. Met. Further, in order to maintain the ammonia concentration of the basic aqueous solution at about 9 g / L and the pH of the basic aqueous solution at about 12.0 to 12.2, a 16 mass% aqueous solution of sodium hydroxide and an aqueous 3 mass% solution of ammonia were added to the reaction vessel. Were appropriately supplied. And the 1st primary particle which contains nickel, cobalt, and manganese by molar ratio 6: 2: 2 was formed.

  The first primary particles were separated by filtration and washed with water. The first primary particles after washing were heated at 300 ° C. for 20 hours and dehydrated to obtain a first dehydrated product.

  Nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in water to prepare a second aqueous solution having a molar ratio of nickel, cobalt and manganese of 4: 2: 4. The total concentration of nickel, cobalt and manganese in the second aqueous solution was 0.9 mol / L.

  Water was put into a reaction vessel equipped with a stirrer and a nitrogen introduction tube, and heated to 40 ° C. with stirring. Nitrogen was continuously supplied from the nitrogen introduction tube, and the reaction vessel was maintained under a nitrogen atmosphere. Sodium hydroxide 16 mass% aqueous solution and ammonia 28 mass% aqueous solution were supplied to the reaction tank, and basic aqueous solution with ammonia concentration of 9 g / L and pH of 12.4 was prepared.

  Said 2nd aqueous solution was supplied with respect to the basic aqueous solution made into stirring conditions with a speed | rate of 1000 rpm. The supply rate of the second aqueous solution was 0.4 mL / min. Met. Further, in order to maintain the ammonia concentration of the basic aqueous solution at about 9 g / L and the pH of the basic aqueous solution at about 12.0 to 12.2, a 16 mass% aqueous solution of sodium hydroxide and an aqueous 3 mass% solution of ammonia were added to the reaction vessel. Were appropriately supplied. Then, second primary particles containing nickel, cobalt, and manganese at a molar ratio of 4: 2: 4 were formed.

  The second primary particles were separated by filtration and washed with water. The washed second primary particles were heated at 300 ° C. for 20 hours and dehydrated to obtain a second dehydrated product.

  25 g of the first dehydrated product and 25 g of the second dehydrated product are put into a hybridization system (NHS) manufactured by Nara Machinery Co., Ltd. and mixed at 15000 rpm for 5 minutes. Particles were produced.

The above dehydrated bonded particles and lithium carbonate were mixed to obtain a mixture so that the molar ratio of lithium to the total of nickel, cobalt and manganese was 1.1: 1. 0.5% by mass of zirconium phosphate was added to the mixture and mixed. The obtained mixture was subjected to primary firing at 650 ° C. for 10 hours. Next, secondary firing was performed at 850 ° C. for 5 hours to obtain a fired product. The fired product was cooled, pulverized and classified to obtain a lithium composite metal oxide having an average particle size of 6 μm. This was used as the active material of Example 3. The active material of Example 3 has an average composition represented by Li _1.13 Ni _{4.97 / 10} Co _{1.99 / 10} Mn _{2.98 / 10} Zr _{0.05 / 10} O ₂ .

Example 4
The lithium ion secondary battery of Example 4 was produced as follows.

  The positive electrode was prepared 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 active material of Example 1, 3 parts by mass of acetylene black as a conductive auxiliary agent, 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 with a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and a positive electrode having a thickness of about 60 μm was obtained.

  The negative electrode was produced as follows.

  Mix 97 parts by weight of graphite powder, 1 part by weight of acetylene black as a conductive additive, 1 part by weight of styrene-butadiene rubber (SBR) and 1 part by weight of carboxymethyl cellulose (CMC) as a binder, and add an appropriate amount of this mixture. A slurry was prepared by dispersing in ion exchange water. The slurry was applied to a negative electrode current collector copper foil having a thickness of 20 μm so as to form a film using a doctor blade, and the current collector coated with the slurry was dried and pressed, and the joined product was heated at 200 ° C. at 2 ° C. It was heated with a vacuum dryer for a time, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and a negative electrode having a thickness of about 45 μm was obtained.

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 polypropylene resin as a separator 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 in which LiPF ₆ was dissolved at 1 mol / L in a solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 3: 7 (volume ratio) was used. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. Note that 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 laminated lithium ion secondary battery.

  Through the above steps, a laminate type lithium ion secondary battery of Example 4 was produced.

(Example 5)
A laminated lithium ion secondary battery of Example 5 was produced in the same manner as in Example 4 except that the active material of Example 2 was adopted instead of the active material of Example 1.

(Comparative Example 1)
A laminated lithium ion secondary battery of Comparative Example 1 was produced in the same manner as in Example 4 except that commercially available LiNi _5/10 Co _2/10 Mn _3/10 O ₂ was used as the active material.

<Evaluation example 1> Analysis of active material About the active material primary particle of the active material of Example 1, a cross section is formed by an Ar ion milling method using an ion slicer (EM-09100IS, manufactured by JEOL Ltd.). The cross section was measured at an acceleration voltage of 200 kV while performing spherical aberration correction using a high angle scattering annular dark field scanning transmission electron microscope (HAADF-STEM): JEM-ARM200F (JEOL: manufactured by JEOL Ltd.). The obtained HAADF-STEM image is shown in FIG. In the HAADF-STEM image of FIG. 6, no crystal grain boundary indicating that the crystal orientation is different was observed.

  The cross section of the same primary particles of the active material as described above was analyzed using STEM-EDX in which a scanning transmission electron microscope and an energy dispersive X-ray spectrometer were combined, with Co and Mn as measurement targets. FIG. 7 shows a diagram in which the element maps of Co and Mn obtained by STEM-EDX and the HAADF-STEM image are superimposed. Furthermore, the figure which divided each composition part with the continuous line is shown in FIG. The composition parts divided by a solid line in FIG. 8 are, in order from the top, the second composition part, the first composition part, the second composition part, the first composition part, and the second composition part.

  The cross section of the same primary particle of the active material as above was measured with a low angle scattering annular dark field scanning transmission electron microscope (LAADF-STEM). Compared with the HAADF-STEM image, the LAADF-STEM image can clearly display the diffraction contrast and visualize the distortion inherent in the crystal. The obtained LAADF-STEM image is shown in FIG. In FIG. 9, white lines that were not observed in FIG. 6 were observed. The white line portion that crosses the center of the particle corresponds to the interface portion between the second composition part and the first composition part.

  The cross section of the same active material primary particle as the above was measured with a bright field scanning transmission electron microscope (BF-STEM). The obtained BF-STEM image is shown in FIG. In the BF-STEM image of FIG. 10, the vertical direction is the orientation <0001>, and the horizontal direction is the orientation <11-20>. In <11-20>, “−2” represents 2 with an overline. The image of FIG. 10 and the image of FIG. 9 are in the relationship of reversal of the image contrast, and the white line first confirmed in FIG. 9 is observed as a black line in FIG.

  Subsequently, in the BF-STEM image of FIG. 10, the black line portion crossing the center was measured with an annular bright field scanning transmission electron microscope (ABF-STEM). This black line location corresponds to the interface location between the second composition part and the first composition part. The obtained ABF-STEM image is shown in FIG. As a comparison, FIG. 12 shows an ABF-STEM image obtained by measuring the vicinity of the center of the first composition part with an annular bright-field scanning transmission electron microscope.

  In FIG.11 and FIG.12, each spot shows an element and the spot layer of a horizontal direction shows an element layer. And the darkest black spot layer shows a transition metal layer. Each image in FIG. 11 and FIG. 12 is regularly repeated in the order of the transition metal layer, which is the darkest black spot layer, hereinafter, the oxygen layer, the lithium layer, the oxygen layer, and the transition metal layer in the vertical direction. Recognize. When FIG. 11 and FIG. 12 are observed and compared in detail, in FIG. 12, the layers composed of each element are arranged in a straight line without any disturbance, whereas each layer in FIG. 11 has a very slight arrangement disturbance. I understand. However, no special boundary was observed in the periodic element arrangement of FIG. 11 despite the fact that the composition was switched as confirmed in FIGS. This means that the image of FIG. 11 has a single crystal structure. That is, the interface part between the second composition part and the first composition part of the primary particles of the active material is a place where only the transition metal composition is switched without substantially different from other parts from the viewpoint of the crystal lattice. Means that. Since no image showing the boundary of the crystal was observed in FIG. 11, the newly observed line due to the diffraction contrast in FIGS. 9 and 10 does not indicate a crystal grain, but a very small amount of primary particles of the active material. It is thought that the disorder of the arrangement was observed as an image, and the cause is presumed to be the distortion generated due to the composition change.

  From the results shown in FIGS. 6 to 12, the active material primary particles composed of the first composition part and the second composition part have single parts that appear as if they are single crystals, although there are portions where the compositions are partially different. It was confirmed that it was a single crystal structure.

  In addition, the cross section of the primary particles of the active material was analyzed using STEM-EDX and Zr as a measurement target. As a result, it was confirmed that Zr was present at a higher concentration on the surface layer side than on the inner side of the particles.

<Evaluation Example 2> Evaluation of Lithium Ion Secondary Battery The following tests were conducted on the laminated lithium ion secondary batteries of Examples 4 and 5 and Comparative Example 1. The battery to be measured is CCCV charged (constant current constant voltage charge) at 25 ° C., 0.33 C rate, voltage 4.5 V, and CC discharge (constant current discharge) is performed at voltage 3.0 V, 0.33 C rate. The discharge capacity as measured was measured. This discharge capacity was taken as the initial capacity.

  Furthermore, CCCV charge (constant current constant voltage charge) is performed at 60 ° C., 1 C rate, voltage 4.5 V, and after 2.5 hours, CC discharge (constant current discharge) is performed at voltage 3.0 V, 1 C rate 4 A charge / discharge cycle of 0.5 V to 3.0 V was performed on the battery to be measured for 100 cycles and 200 cycles, and then the discharge capacity at the 0.33 C rate was measured to calculate the capacity retention rate.

The capacity retention rate (%) was obtained by the following formula.
Capacity maintenance rate (%) = 100 or discharge capacity after 200 cycles / initial capacity × 100
For example, the current rate for discharging in 1 hour is referred to as 1C.

  The results are shown in Table 2. The test result is an average value of n = 2.

  It can be seen that the lithium ion secondary batteries of Examples 4 and 5 show an excellent capacity retention rate as compared with the lithium ion secondary battery of Comparative Example 1. The difference in capacity retention rate of these batteries is based on the difference in active materials. Experiments have confirmed that deterioration of the active material of the present invention is suppressed. In addition, it has been experimentally confirmed that the active material of the present invention is more suitable due to the presence of the doping element represented by D in the general formula.

1: first aqueous solution, 11: first particle nucleus, 12: first primary particle,
2: second aqueous solution, 21: second particle nucleus, 22: second primary particle,
3: Basic aqueous solution,
4: A bonded particle in which the first primary particle and the second primary particle are bonded to each other.

Claims (6)

General formula: Lia ₁ Nib ₁ Coc ₁ Mnd ₁ De ₁ Of ₁ (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, At least one element selected from Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, and Rf, 1.7 ≦ f1 ≦ 2.1 ) And a general formula: Li _a2 Ni _b2 Co _c2 Mn _d2 D _e2 O _f2 (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe , Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf Element, 1.7 ≦ f2 ≦ 2.1, but at least c2 <c Or an active material having a second composition unit represented by d2> d1 satisfies either),
The active material, wherein the first composition part and the second composition part are delocalized. General formula: Lia ₁ Nib ₁ Coc ₁ Mnd ₁ De ₁ Of ₁ (0.2 ≦ a1 ≦ 1.5, b1 + c1 + d1 + e1 = 1, 0 ≦ e1 <1, D is Fe, Cr, Cu, Zn, Ca, Mg, At least one element selected from Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, and Rf, 1.7 ≦ f1 ≦ 2.1 ) And a general formula: Li _a2 Ni _b2 Co _c2 Mn _d2 D _e2 O _f2 (0.2 ≦ a2 ≦ 1.5, b2 + c2 + d2 + e2 = 1, 0 ≦ e2 <1, D is Fe , Cr, Cu, Zn, Ca, Mg, Zr, S, Si, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, Rf Element, 1.7 ≦ f2 ≦ 2.1, but at least c2 <c Or an active material having a second composition unit represented by d2> d1 satisfies either),
An active material, wherein the first composition part and the second composition part form primary particles of an active material as a single crystal structure.   The first composition part and the second composition part are delocalized, and the first composition part and the second composition part form active material primary particles as a single crystal structure. The active material according to claim 1 or 2, wherein a) Step of preparing a first aqueous solution in which nickel salt, cobalt salt and manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b3: c3: d3 (b3 + c3 + d3 = 10) b) Nickel salt, cobalt A second aqueous solution in which a salt and a manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b4: c4: d4 (b4 + c4 + d4 = 10, but at least satisfies either c4 <c3 or d4> d3) The step of preparing,
c) Step of preparing a basic aqueous solution d) First primary solution containing nickel, cobalt and manganese in a molar ratio b3: c3: d3 simultaneously supplying the first aqueous solution and the second aqueous solution to the basic aqueous solution. A step of forming particles and second primary particles comprising nickel, cobalt and manganese in a molar ratio of b4: c4: d4; e) the first primary particles and the second primary particles bonded together; The process of forming a coupling | bonding particle f) The manufacturing method of the active material in any one of Claims 1-3 including the baking process which mixes the said coupling | bonding particle and lithium salt, and bakes. a) Step of preparing a first aqueous solution in which nickel salt, cobalt salt and manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b3: c3: d3 (b3 + c3 + d3 = 10) b) Nickel salt, cobalt A second aqueous solution in which a salt and a manganese salt are dissolved in water and the molar ratio of nickel, cobalt and manganese is b4: c4: d4 (b4 + c4 + d4 = 10, but at least satisfies either c4 <c3 or d4> d3) C) Step of preparing a basic aqueous solution g) The first aqueous solution is supplied to the basic aqueous solution, and first primary particles containing nickel, cobalt and manganese in a molar ratio b3: c3: d3 are provided. Forming step h) heating the first primary particles to form a first dehydrated product i) supplying the second aqueous solution to the basic aqueous solution; J) a step of forming second primary particles containing ru, cobalt and manganese in a molar ratio of b4: c4: d4 j) a step of heating the second primary particles to form a second dehydrated k) particle composite In the apparatus, the first dehydrated product and the second dehydrated product are mixed to produce dehydrated bonded particles in which the first dehydrated product and the second dehydrated product are bonded to each other. L) The dehydrated bonded particles and lithium salt The manufacturing method of the active material in any one of Claims 1-3 including the baking process which mixes and bakes.   The lithium ion secondary battery which comprises the active material of the active material of Claims 1-3, or the active material obtained by the manufacturing method of Claims 4-5.