JP2014072072A - Positive electrode active material for nonaqueous electrolyte secondary battery, method for producing the same, and positive electrode for nonaqueous electrolyte secondary battery manufactured using the positive electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a positive electrode active material for a nonaqueous electrolyte secondary battery, improving initial discharge capacity and capable of suppressing deterioration in average operating voltage; a method for producing the positive electrode active material for a nonaqueous electrolyte secondary battery; and a positive electrode for a nonaqueous electrolyte secondary battery manufactured using the positive electrode active material.SOLUTION: A positive electrode active material for a nonaqueous electrolyte secondary battery comprises: a lithium transition metal composite oxide 21 that contains at least lithium, nickel and manganese and has a layered structure; and a compound 22 of a rare earth element adhering on at least a part of the surface of the lithium transition metal composite oxide 21. The average particle size of the compound 22 of a rare earth element is more than 100 nm and 500 nm or less.

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a positive electrode for a non-aqueous electrolyte secondary battery using the positive electrode active material.

  In recent years, mobile information terminals such as mobile phones, notebook personal computers, and PDAs have been rapidly reduced in size and weight, and batteries as drive power sources are required to have higher capacities. Lithium ion batteries that charge and discharge by moving lithium ions between positive and negative electrodes have high energy density and high capacity, and are therefore widely used as drive power sources for such mobile information terminals. .

Here, the mobile information terminal has a tendency to further increase power consumption with enhancement of functions such as a video playback function and a game function, and a further increase in capacity is strongly desired. As a measure to increase the capacity of the non-aqueous electrolyte secondary battery, in addition to a measure to increase the capacity of the active material and a measure to increase the filling amount of the active material per unit volume, the charge voltage of the battery is increased. There are measures. However, when the charging voltage of the battery is increased, the reaction between the positive electrode active material and the nonaqueous electrolytic solution tends to occur.
Thus, it has been shown that the reaction between the positive electrode active material and the non-aqueous electrolyte can be suppressed when the charging voltage is increased by coating the surface of the positive electrode active material with a compound (Patent Documents 1 and 2 below). reference).

WO2010 / 004973A1 WO2005 / 008812A1

  The above-mentioned Patent Document 1 mainly aims to suppress the reaction between the positive electrode active material and the non-aqueous electrolyte when the charge voltage is increased using lithium cobalt oxide as the main active material. However, lithium cobaltate has a problem of high cost because cobalt is a rare metal. Therefore, recently, the cost has been kept low by using a composite oxide of lithium cobalt nickel manganese for the positive electrode active material instead of lithium cobalt oxide.

  Also for the lithium cobalt nickel manganese composite oxide, the reaction between the positive electrode active material and the non-aqueous electrolyte can be suppressed by attaching a rare earth element compound to the surface as in Patent Document 1 described above. In Patent Document 2, by adding a group 3 element of the periodic table to the surface of the lithium cobalt nickel manganese composite oxide, the reaction with the non-aqueous electrolyte is suppressed, and side reactions and cycle characteristics during storage. Is disclosed to be improved. However, when an element is deposited on the surface of the lithium cobalt nickel manganese composite oxide in this way, the deposited element inhibits lithium diffusion, resulting in an increase in resistance. As a result, there has been a problem that the operating voltage at the time of discharging is lowered and the energy density of the battery is lowered.

  The positive electrode active material according to one aspect of the present invention contains at least lithium, nickel, and manganese, and has a layered structure and is attached to a part of the surface of the lithium transition metal composite oxide. And an average particle size of the rare earth element compound is more than 100 nm and not more than 500 nm.

  According to one aspect of the present invention, a positive electrode active material having a high discharge voltage and a high capacity can be obtained.

Explanatory drawing which shows the surface state of the nickel cobalt lithium manganate of 1 aspect of this invention. Explanatory drawing which shows the surface state different from the surface state of the nickel cobalt lithium manganate of 1 aspect of this invention. Explanatory drawing which shows the three-electrode-type beaker cell of 1 aspect of this invention.

  The positive electrode active material according to one aspect of the present invention contains at least lithium, nickel, and manganese, and has a layered structure and is attached to a part of the surface of the lithium transition metal composite oxide. And an average particle size of the rare earth element compound is more than 100 nm and not more than 500 nm.

  If it is the said structure, the operating voltage fall at the time of discharge can be suppressed, and reaction with a non-aqueous electrolyte and lithium transition metal complex oxide can also be suppressed. As a result, a positive electrode active material having a high discharge voltage and a high capacity, that is, a high energy density can be obtained. This mechanism is not clear, but is thought to be due to the following factors. If the average particle size of the rare earth element compound is regulated to more than 100 nm and 500 nm or less, it is possible to reduce the inhibition of lithium diffusion by the rare earth element compound. In addition, if a rare earth element compound adheres to the surface of the lithium transition metal composite oxide, the decomposition reaction of the electrolytic solution can be suppressed, so a coating with low lithium ion permeability is formed on the surface of the lithium transition metal composite oxide. It is thought that it originates in being able to suppress forming.

  Here, the state in which the compound of the rare earth element is attached to a part of the surface of the lithium transition metal composite oxide refers to the compound of the rare earth element on the surface of the lithium transition metal composite oxide 21 as shown in FIG. This means that 22 is attached. That is, in this state, as shown in FIG. 2, the lithium transition metal composite oxide 21 and the rare earth element compound 22 are simply mixed, and a part of the rare earth element compound 22 becomes the lithium transition metal composite oxide 21. It does not include the state where it happens to contact.

The average particle size of the rare earth element compound is more than 100 nm and not more than 500 nm. When the average particle size of the rare earth element compound is 100 nm or less, the surface of the lithium transition metal composite oxide is finely and temporarily covered, so that lithium diffusion is inhibited. For this reason, the resistance at the positive electrode increases, and the discharge voltage decreases. Further, if the average particle size of the rare earth element compound exceeds 500 nm, the adhesion site of the rare earth element compound is partially biased, and the reaction with the non-aqueous electrolyte cannot be sufficiently suppressed. In consideration of this, the average particle size of the rare earth element compound is particularly preferably 120 nm or more and 300 nm or less. This is because with such an average particle diameter, the decomposition reaction of the electrolytic solution by the rare earth element compound can be sufficiently suppressed, and a decrease in the discharge voltage can also be suppressed.
The average particle diameter of the rare earth element compound is a value obtained from an SEM image of the positive electrode active material.

The composition formula of the lithium transition metal composite oxide containing Li, Ni, and Mn and having a layered structure is represented by the chemical formula Li _{1 + x} (Ni _a Mn _b Co _c ) O ₂ (x + a + b + c = 1, 0 <x ≦ 0. 1, 0 ≦ c <0.4, ab> 0.035, 0.035 <a ≦ 0.85, 0 <b ≦ 0.5).
When x exceeds 0.1, the ratio of the transition metal that undergoes the oxidation-reduction reaction during charge / discharge decreases, and the charge / discharge capacity decreases. Therefore, x is preferably 0.1 or less. The reason why 0 ≦ c <0.4 is that when c is 0.4 or more, the content of cobalt, which is a rare metal, increases too much, which is disadvantageous in terms of cost. The reason for setting ab> 0.035 is due to the following two reasons. First, when the composition ratio of Mn is high, an impurity phase is generated, which leads to a decrease in capacity and a decrease in output. Therefore, ab is preferably 0 or more. Secondly, the higher the Ni composition ratio, the larger the capacity per weight of the positive electrode active material. Therefore, it is desirable that the Ni composition ratio is as high as possible.
In view of the balance of battery characteristics, nickel cobalt lithium manganate containing three components of nickel, cobalt, and manganese is most preferable, and 0 <c <0.4 is more preferable.

The adhesion amount of the rare earth element compound is preferably 0.005 mass% or more and 0.8 mass% or less with respect to the lithium transition metal composite oxide in terms of rare earth elements, and particularly 0.01 mass%. The content is preferably 0.5% by mass or less.
If the adhesion amount of the rare earth element compound is less than 0.005% by mass, the effect of suppressing the reaction between the non-aqueous electrolyte and the positive electrode active material is small. If the adhesion amount exceeds 0.8% by mass, the rare earth compound is Since the surface of the positive electrode active material is excessively covered, lithium diffusion may be inhibited, and as a result, the discharge voltage of the battery may be lowered.

  Examples of the method of attaching the rare earth element compound to a part of the surface of the lithium transition metal composite oxide include, for example, the first step of attaching the rare earth element compound to the surface of the lithium transition metal composite oxide; And a second step of heat-treating the lithium transition metal composite oxide at a temperature exceeding 700 ° C. Further, as the first step, in the solution in which the lithium transition metal composite oxide is dispersed, a rare earth element compound (to distinguish from the rare earth element compound attached to a part of the surface of the lithium transition metal composite oxide). Hereinafter referred to as a rare earth element compound as a raw material), or a method of spraying a solution containing a rare earth element compound as a raw material while mixing a lithium transition metal composite oxide powder. Obtained by etc.

By the first step, the rare earth element compound (usually a rare earth element hydroxide) can be attached to a part of the surface of the lithium transition metal composite oxide. In this case, the average particle size of the rare earth element compound is less than 100 nm. In the second step, when heat treatment is performed at a temperature exceeding 700 ° C., the rare earth element compound having an average particle diameter of less than 100 nm grows so that the average particle diameter exceeds 100 nm and is 500 nm or less. To do. In addition, this heat treatment may cause a chemical change in the rare earth element compound (usually, when the heat treatment is performed at a temperature of 500 ° C. or higher, the rare earth element hydroxide is a rare earth oxyhydroxide. Most of them are converted to rare earth oxides, although a small amount of oxyhydroxide may exist without changing to rare earth oxides.)
The heat treatment temperature in the second step is desirably 1000 ° C. or lower. This is because if the heat treatment temperature exceeds 1000 ° C., the average particle size of the rare earth element compound may exceed 500 nm, and the reaction between the non-aqueous electrolyte and the lithium transition metal composite oxide cannot be sufficiently suppressed.

  As the rare earth element compound as the raw material, a rare earth element acetate, a rare earth element nitrate, a rare earth element sulfate, a rare earth element oxide, a rare earth element chloride, or the like can be used.

  Since some lithium components remaining on the surface of the positive electrode active material and lithium of the lithium transition metal composite oxide on the surface layer of the positive electrode active material may react with the rare earth element compound during the heat treatment, Some may contain lithium ions. In this case, the same effect as described above can be obtained.

(Other matters)
(1) Examples of the lithium transition metal composite oxide include lithium nickel cobalt manganate, and the nickel cobalt lithium manganate has a molar ratio of nickel, cobalt, and manganese of 4: 3: 3, 5: 2. : 3, 5: 3: 2, 6: 2: 2, 7: 1: 2, 7: 2: 1, 8: 1: 1, and the like.

(2) The solvent of the nonaqueous electrolyte used in one aspect of the present invention is not limited, and a solvent that has been conventionally used in nonaqueous electrolyte secondary batteries can be used. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, propionic acid Compounds containing esters such as ethyl and γ-butyrolactone, compounds containing sulfone groups such as propane sultone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, 1,4 -Compounds containing ethers such as dioxane and 2-methyltetrahydrofuran, butyronitrile, valeronitrile, n-heptanenitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronite Le, 1,2,3-propanetriol-carbonitrile, 1,3,5-pentanetricarboxylic carbonitrile compounds containing nitrile such as nitrile or can be used compounds comprising an amide such as dimethylformamide. In particular, a solvent in which a part of these H is substituted with F is preferably used.
Further, these can be used alone or in combination, and a solvent in which a cyclic carbonate and a chain carbonate are combined, and a solvent in which a compound containing a small amount of nitrile or an ether is further combined with these is preferable. .

Solutes of the non-aqueous electrolyte include LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiPF _6-x (C _n F _{2n + 1} ) _x [wherein 1 <x <6, n = 1 or 2], or a lithium salt having an oxalato complex as an anion can also be used. As a lithium salt having this oxalato complex as an anion, in addition to LiBOB [lithium-bisoxalate borate], a lithium salt having an anion in which C ₂ O ₄ ²⁻ is coordinated to the central atom, for example, Li [M (C ₂ O ₄ ) _x R _y ] (wherein M is a transition metal, an element selected from groups IIIb, IVb, and Vb of the periodic table, R is selected from a halogen, an alkyl group, and a halogen-substituted alkyl group) Group, x is a positive integer, and y is 0 or a positive integer). Specifically, there are Li [B (C ₂ O ₄ ) F ₂ ], Li [P (C ₂ O ₄ ) F ₄ ], Li [P (C ₂ O ₄ ) ₂ F ₂ ], and the like. However, it is most preferable to use LiBOB in order to form a stable film on the surface of the negative electrode even in a high temperature environment.

  In addition, the said solute may be used not only independently but in mixture of 2 or more types. Further, the concentration of the solute is not particularly limited, but is preferably 0.8 to 1.7 mol per liter of the electrolytic solution. Furthermore, in applications that require discharging with a large current, the concentration of the solute is desirably 1.0 to 1.6 mol per liter of the electrolyte.

(3) As the negative electrode active material used in one aspect of the present invention, conventionally used negative electrode active materials can be used, and in particular, carbon materials capable of occluding and releasing lithium, or alloys with lithium can be formed. A metal, an alloy containing the metal, an alloy compound thereof, a mixture thereof, or the like can be given.
As the carbon material, natural graphite, non-graphitizable carbon, graphite such as artificial graphite, coke, and the like can be used. As the metal that can form an alloy with lithium, silicon, tin, and oxygen can be used. Examples thereof include silicon oxide and tin oxide that are bonded to each other. Moreover, what mixed the said carbon material and the compound of silicon or tin can also be used.

(4) At the interface between the positive electrode and the separator or at the interface between the negative electrode and the separator, a layer made of an inorganic filler that has been conventionally used can be formed. As the filler, it is possible to use oxides or phosphate compounds using titanium, aluminum, silicon, magnesium, etc., which have been used conventionally, or those whose surfaces are treated with hydroxide or the like. .
The filler layer may be formed by directly applying a filler-containing slurry to the positive electrode, negative electrode, or separator, or by attaching a filler-formed sheet to the positive electrode, negative electrode, or separator. Can do.

(5) As a separator used in one aspect of the present invention, a conventionally used separator can be used. Specifically, not only a separator made of polyethylene, but also a material in which a layer made of polypropylene is formed on the surface of a polyethylene layer, or a material in which a resin such as an aramid resin is applied to the surface of a polyethylene separator is used. Also good.

(6) In the following examples, experimental data in the case of using erbium as the desired earth element was put, but not limited thereto, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, thulium, ytterbium It is considered that the same effect can be obtained with lutetium, yttrium, lanthanum, scandium, and cerium. That is, even if these rare earth element compounds are attached to the surface of the lithium transition metal composite oxide so that the average particle diameter exceeds 100 nm and becomes 500 nm or less, it is considered that the same effect as the following erbium can be exhibited. . The rare earth element compound may be a compound of at least one element selected from rare earth elements.

  The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the production method thereof, and the positive electrode using the positive electrode active material are not limited to those shown in the following embodiments, and are appropriately changed within the scope not changing the gist thereof Can be implemented.

(Example)
[Production of positive electrode]
Li ₂ CO ₃ and a coprecipitated hydroxide represented by Ni _0.55 Co _0.20 Mn _0.25 (OH) ₂ have a molar ratio of Li to the entire transition metal of 1.08: 1. So that it was mixed in an Ishikawa style mortar. Next, the mixture was pulverized after heat treatment at 950 ° C. for 20 hours in an air atmosphere, whereby Li _1.04 Ni _0.53 Co _0.19 Mn _0.24 O ₂ having an average secondary particle diameter of about 17 μm. The nickel cobalt lithium manganate represented by this was obtained.

1000 g of the nickel cobalt manganate particles were prepared, and the particles were added to 3.0 L of pure water and stirred to prepare a suspension in which nickel cobalt lithium manganate was dispersed. Next, a solution in which 3.15 g of erbium nitrate pentahydrate [Er (NO ₃ ) ₃ .5H ₂ O] was dissolved in 200 mL of pure water was added to this suspension. At this time, a 10% by mass nitric acid aqueous solution or a 10% by mass sodium hydroxide aqueous solution was appropriately added in order to adjust the pH of the suspension in which nickel cobalt lithium manganate was dispersed to be 9.

  Next, after completion of the addition of the erbium nitrate pentahydrate solution, suction filtration and further washing with water, the obtained powder was dried at 120 ° C., and water was partially added to the surface of the lithium nickel cobalt manganate. The thing to which erbium oxide adhered was obtained. When observed with a scanning electron microscope (SEM), the average particle diameter of erbium hydroxide was found to be 10 nm. Thereafter, the obtained powder was heat-treated in air at 800 ° C. for 8 hours to produce a positive electrode active material.

When the obtained positive electrode active material was observed with a scanning electron microscope (SEM), it was found that an erbium compound having an average particle diameter of 200 nm was adhered to a part of the surface of lithium nickel cobalt manganate. . Moreover, when the adhesion amount of the erbium compound was measured by ICP, it was 0.20 mass% with respect to lithium nickel cobalt manganate in terms of erbium element. Furthermore, when the BET value of the obtained positive electrode active material was measured, it was 0.22 m ² / g. In addition, most of the erbium compound after the heat treatment was erbium oxide.

  The positive electrode active material thus obtained was mixed with carbon powder as a positive electrode conductive agent, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone as a dispersion medium. The material, the positive electrode conductive agent, and the binder were added so that the mass ratio was 95: 2.5: 2.5, and then kneaded to prepare a positive electrode slurry. Finally, this positive electrode slurry is applied to both sides of a positive electrode current collector made of aluminum foil, dried, rolled by a rolling roller, and further, positive electrode current collector tabs are attached to the positive electrode current collector on both sides. A positive electrode on which a mixture layer was formed was obtained.

[Production of three-electrode beaker cell]
Using the positive electrode produced as described above, a three-electrode beaker cell shown in FIG. 3 was produced. Specifically, the positive electrode is a working electrode 31, lithium metal is used for the counter electrode 32 and the reference electrode 33, and the electrolyte solution 34 has a volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of 3: 7. A solution obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) so as to have a concentration of 1.0 mol / liter with respect to the mixed solvent mixed in ( ₁ ) was used.
The three-electrode beaker cell produced as described above is hereinafter referred to as cell A.

(Comparative Example 1)
A three-electrode beaker cell was produced in the same manner as in the above example except that lithium nickel cobalt manganate having no erbium compound attached to the surface was used as the positive electrode active material. The BET value of this positive electrode active material was measured and found to be 0.23 m ² / g.
The three-electrode beaker cell produced in this way is hereinafter referred to as cell Z1.

(Comparative Example 2)
When producing the positive electrode active material, a three-electrode beaker cell was produced in the same manner as in the above example except that the heat treatment after drying was performed at 300 ° C. The BET value of the obtained positive electrode active material was measured and found to be 0.82 m ² / g. Moreover, when the magnitude | size of the compound adhering to the surface was measured from the SEM image of this positive electrode active material, the average particle diameter was 10 nm. Furthermore, most of the erbium compound after the heat treatment was erbium oxyhydroxide.
The three-electrode beaker cell thus produced is hereinafter referred to as cell Z2.

(Comparative Example 3)
When producing the positive electrode active material, a three-electrode beaker cell was produced in the same manner as in the above example except that the heat treatment after drying was performed at 500 ° C. The BET value of the obtained positive electrode active material was measured to be 0.61 m ² / g. Moreover, when the magnitude | size of the compound adhering to the surface was measured from the SEM image of this positive electrode active material, the average particle diameter was 20 nm. Further, most of the erbium compound after the heat treatment was erbium oxide.
The three-electrode beaker cell thus produced is hereinafter referred to as cell Z3.

(Experiment 1)
The cell A, was charged to 4.5V (vs.Li/Li ⁺⁾ at a current density of 0.75 mA / cm ² and Z1 to Z3, 4.5V at a current density of 0.08mA / cm ² (vs. Li / Li ⁺ ) was charged. Next, the battery was discharged at a current density of 0.75 mA / cm ² to 2.75 V (vs. Li / Li ⁺ ), and the initial discharge specific capacity (mAh / g) and average discharge (operation) voltage of the positive electrode active material were Asked.
The pause interval between the charge and discharge was 10 minutes.

As is apparent from Table 1, the discharge capacity of cell A is equal to or higher than that of cells Z2 and Z3, and the average operating (discharge) voltage of the first cycle is higher. Is recognized. This is considered to be due to the following reasons.
When the Er compound attached to the surface of the lithium transition metal composite oxide is heat-treated at 300 ° C. or 500 ° C. (in the case of cells Z2 and Z3), the average particle size of the Er compound after heat treatment is 100 nm or less (specifically 10 nm and 20 nm), and the average particle diameter of the Er compound did not change much before and after the heat treatment. In contrast, when the Er compound is heat-treated at 800 ° C. (in the case of cell A), the average particle diameter of the Er compound exceeds 100 nm (specifically, 200 nm) after the heat treatment, and the heat treatment is performed after the heat treatment. Compared to before, the average particle size of the Er compound was rapidly increased. As described above, in the cell A in which the Er compound is grown by the heat treatment and the average particle size is increased, the Er compound can be prevented from being excessively coated on the surface of the lithium transition metal composite oxide. Therefore, the side reaction between the lithium transition metal composite oxide and the electrolytic solution can be reliably suppressed without inhibiting the diffusion of lithium. On the other hand, in the cells Z2 and Z3 in which the average particle diameter does not change much even when the Er compound is heat-treated, it is not possible to prevent the Er compound from covering the surface of the lithium transition metal composite oxide excessively. Therefore, the side reaction between the lithium transition metal composite oxide and the electrolytic solution can be suppressed, but it is considered that the diffusion of lithium is inhibited.

  Moreover, it is recognized that the cell A has a higher average operating voltage than the cell Z1 in which the Er compound is not attached to the surface of the lithium transition metal composite oxide. This is because, in the cell Z1 in which no Er compound is present on the surface of the lithium transition metal composite oxide, the electrolytic solution is decomposed, and a film having low lithium ion conductivity is formed on the surface of the lithium transition metal composite oxide. On the other hand, in the cell A in which an Er compound is present on the surface of the lithium transition metal composite oxide, decomposition of the electrolytic solution is suppressed. Therefore, it is thought that it is possible to suppress the formation of a film having low lithium ion conductivity on the surface of the lithium transition metal composite oxide.

(Experiment 2)
Table 2 shows the relationship between the heat treatment temperature after the Er compound was attached to the surface of the lithium transition metal composite oxide and the average particle size of the Er compound after the heat treatment.

  As is apparent from Table 2, when the heat treatment temperature is 700 ° C. or less, the average particle diameter of the Er compound is 100 nm or less even after the heat treatment, and the average particle diameter of the Er compound greatly changes before and after the heat treatment. It is recognized that he did not. On the other hand, when the heat treatment temperature is 800 ° C., the average particle diameter of the Er compound is 200 nm after the heat treatment, and it is recognized that the average particle diameter of the Er compound is significantly larger than that before the heat treatment. It is done. Therefore, it can be seen that heat treatment must be performed at a temperature exceeding 700 ° C. in order to increase the average particle size of the Er compound.

  The present invention is also applied to a drive power source for mobile information terminals such as mobile phones, notebook computers, and PDAs, a drive power source for high output such as HEV and electric tools, and a storage battery device combined with a solar cell or a power system. Can be expected.

21: Lithium transition metal composite oxide 22: Rare earth element compound 31: Working electrode 32: Counter electrode (lithium metal)
33: Reference electrode (lithium metal)
34: Electrolytic solution

Claims (8)

A lithium transition metal composite oxide containing at least lithium, nickel, and manganese and having a layered structure;
A rare earth element compound adhering to a part of the surface of the lithium transition metal composite oxide;
Including
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein an average particle diameter of the rare earth element compound is more than 100 nm and 500 nm or less.   The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the rare earth element compound includes a rare earth element oxide.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the rare earth element compound has an average particle size of 120 nm or more and 300 nm or less. The lithium transition metal composite oxide has a chemical formula: Li _{1 + X} (Ni _a Mn _b Co _c ) O ₂ (x + a + b + c = 1, 0 <x ≦ 0.1, 0 ≦ c <0.4, a−b> 0. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, represented by 035, 0.035 <a ≦ 0.85, 0 <b ≦ 0.5).   The positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the lithium transition metal composite oxide is lithium nickel cobalt lithium manganate.   The adhesion amount of the rare earth element compound is 0.005 mass% or more and 0.8 mass% or less with respect to the lithium transition metal composite oxide in terms of rare earth elements. The positive electrode active material for nonaqueous electrolyte secondary batteries as described in 2. A first step of attaching a rare earth element compound to the surface of the lithium transition metal composite oxide;
A second step of heat-treating the lithium transition metal composite oxide at a temperature exceeding 700 ° C .;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries which has this. A positive electrode mixture layer comprising the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 6 and a binder;
A positive electrode current collector in which the positive electrode mixture layer is formed on at least one surface;
A positive electrode for a non-aqueous electrolyte secondary battery.

Images