JP2002313337A - Positive electrode active material for use in nonaqueous electrolyte secondary battery and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material or use in a nonaqueous electrolyte secondary battery having increased initial capacity, without impairing formability and filling ability for a positive electrode, and a method for manufacturing it. SOLUTION: A Na-Li-Mn composite oxide is synthesized by mixing a manganese compound raw material comprising a spherical or elliptical secondary particle with a Na compound and a Li compound so as to keep it in shape, and the Na-Li-Mn composite oxide expressed by a formula of Nax [Liy Mn1-y ]O2 (where, 0.66<=x<=1.0, and 0<y<=0.18) is used as a precursor, the precursor is treated in a solution containing a Li ion or molten salt, and thereby a Na ion contained in the precursor is exchanged for a Li ion by ion exchange. The Na-Li-Mn composite oxide is obtained by mixing the Na compound, the Li compound and the Mn compound so that the mol ratio of Na, Li and Mn becomes x:y:1-y (where, 0.66<=x<=1.0, and 0<y<=0.18), and by applying heat treatment at 600<= or more for 10 hours or more and suddenly cooling it to a room temperature of less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same, and more particularly, to improving the moldability and filling properties of an electrode without impairing high cycle characteristics. The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, which can have a high initial capacity as a battery, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the spread of portable devices such as cellular phones and notebook computers, demands for small and lightweight secondary batteries having a high energy density have been increasing. As such a device, a non-aqueous electrolyte type lithium ion secondary battery has been actively developed and put into practical use.

This lithium ion secondary battery has a positive electrode using a lithium-containing composite oxide as an active material, a lithium metal,
Such as lithium alloys, metal oxides or carbon,
The main components are a negative electrode using a material capable of inserting and extracting Li as an active material, and a separator or a solid electrolyte containing a non-aqueous electrolyte.

Among these components, those considered as positive electrode active materials include layered lithium-cobalt composite oxide (LiCoO ₂ ), layered lithium-nickel composite oxide (LiNiO ₂ ), and spinel-type lithium manganese. Composite oxides (LiMn ₂ O ₄ ) and the like can be mentioned.

In particular, in a secondary battery using a layered lithium-cobalt composite oxide for a positive electrode, many developments have been made to obtain excellent initial capacity characteristics and cycle characteristics.
Various results have already been obtained and are now in practical use.
However, since lithium cobalt composite oxide uses rare and expensive Co as a raw material, it is a major cause of an increase in the cost of the positive electrode active material and an increase in the cost of the secondary battery.

A layered lithium-nickel composite oxide using Ni, which is less expensive than Co, is advantageous in terms of cost and capacity, and is being developed as a promising alternative to lithium-cobalt composite oxide. ing. However, secondary batteries using this lithium-nickel composite oxide as the positive electrode active material have the danger of decomposition, heat generation, ignition, etc. when maintained at high temperatures due to the instability of the positive electrode active material in the charged state. However, there are still many issues that need to be solved regarding safety.

The spinel-type lithium manganese composite oxide uses Mn, which is cheaper than Co and Ni, and is excellent in safety in a charged state, so that it is expected as a next-generation cathode material. ing. However, there is a problem that the capacity is smaller than that of the lithium cobalt composite oxide or the lithium nickel composite oxide.

In the spinel-type lithium manganese composite oxide (LiMn ₂ O ₄ ), 3 V (vs. Li ⁺ / Li) and 4 V (vs. Li ⁺ / L) accompanying insertion / desorption of lithium ions.
It is known to have two charge / discharge plateau regions near i). Generally, since charge and discharge are performed using only the 4 V region, a pure stoichiometric Li composed only of Li and Mn is used.
With Mn ₂ O ₄ , only a capacity of about 130 mAh / g can be obtained. Furthermore, since pure LiMn ₂ O ₄ has extremely poor cycle characteristics, measures such as substituting a part of manganese sites with other metal elements are generally taken, but in order to obtain sufficient cycle characteristics. When the replacement amount is increased, the initial capacity is seriously reduced to 100 mAh / g or less.

Even when LiMn ₂ O ₄ is used as an active material, 200 m
A high initial capacity of Ah / g or more can be obtained. However, although a high initial capacity can be obtained, a practical battery cannot be obtained because the capacity greatly deteriorates due to charge / discharge cycles.

On the other hand, unlike the conventional spinel-type lithium manganese composite oxide (LiMn ₂ O ₄ ), LiCoO ₂
Research on a lithium manganese composite oxide (LiMnO ₂ ) having a layered structure similar to that of LiNiO ₂ has been actively conducted.

Since a layered lithium-manganese composite oxide cannot be directly synthesized from a lithium raw material and a manganese raw material by a solid phase method, for example, a layered sodium-manganese composite oxide is solidified as a precursor from a sodium compound and a manganese compound. It is synthesized by a phase method, and is obtained by ion exchange of sodium ions into lithium ions in a solvent or a molten salt at a low temperature of 300 ° C. or lower. When a charge / discharge cycle is performed in a battery using the layered lithium manganese composite oxide in a potential range of 2.0 V to 4.5 V (vs. Li ⁺ / Li), a high initial capacity of 200 mAh / g or more can be obtained. . However, with the charge / discharge cycle, the crystal structure gradually changed to a spinel structure,
Spinel-type lithium manganese composite oxide (LiMn
_{As 2} O ₄ ), charging and discharging are performed using both the 3 V region and the 4 V region, so that the capacity is also greatly reduced.

As a solution to the above problem, Journa
l of the Electrochemical Society, 146 , 3560 (1999) reports that by replacing part of manganese sites with lithium ions, it is possible to obtain O2 type layered lithium manganese composite oxides with high capacity and excellent cycle characteristics. Have been.

The conventional layered lithium manganese composite oxide is composed of O3 in which three manganese oxide layers exist in a unit cell.
It has a mold layered structure. Since the O3-type layered structure has a crystal structure very similar to spinel-type LiMn ₂ O ₄ , manganese ions move during a charge / discharge cycle and change to a spinel structure, resulting in capacity degradation.

On the other hand, the O2-type layered lithium manganese composite oxide has an O2-type layered structure in which two manganese oxide layers exist in a unit cell. To change into a spinel structure, manganese-oxygen is required. The bond must be broken, and spinelization is unlikely to occur. Therefore, it is considered that the cycle characteristics are excellent.

However, according to the above report, the raw material compounds are finely pulverized and mixed at the time of synthesis in order to obtain a uniform compound, so that the density of the positive electrode active material after the synthesis becomes low, and when the electrode is manufactured, the moldability is reduced. There was a problem that deterioration and reduction of the packing density occurred.

[0016]

As described above, in a non-aqueous electrolyte secondary battery using a layered lithium manganese composite oxide as a positive electrode active material, the moldability and filling property as an electrode are maintained while maintaining high cycle characteristics. And it is difficult to provide a high initial capacity as a battery.

The present invention has been made in view of such a problem.
By synthesizing a layered lithium-manganese composite oxide, without impairing the moldability and filling properties of the positive electrode,
An object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery capable of assembling a secondary battery having an improved initial capacity, and a method for producing the same.

[0018]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies and found that an O2 type layered lithium manganese composite oxide in which Mn is partially replaced with Li is used as a positive electrode active material. When applied to, manganese compound raw material primary particles aggregated to form spherical or oval spherical secondary particles, sodium compound and lithium compound so as not to lose its shape, sodium-lithium-manganese composite An oxide is synthesized, and a sodium-ion ion is exchanged for a lithium ion to obtain a lithium-manganese composite oxide. By using the lithium-manganese composite oxide, it has been found that a secondary battery having excellent moldability and filling properties and a large discharge capacity per unit volume can be configured while maintaining high cycle characteristics,
The present invention has been completed.

That is, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a spherical shape or a structure in which primary particles of an O2-type layered lithium manganese composite oxide in which a part of Mn is replaced by Li are aggregated. A manganese compound raw material consisting of spherical or elliptical secondary particles, which is basically made up of elliptical secondary particles and is formed by agglomeration of primary particles, is mixed with a sodium compound and a lithium compound so as not to lose their shape. To obtain a sodium-lithium-manganese composite oxide, and ion-exchange sodium ions contained in the composite oxide into lithium ions.

The crystal structure is represented by space group P3ml, manganese oxide layer is present two layers in the unit cell, the lithium ion is O2 type layered structures present in octahedral sites of the oxide ion, Li _x [ Li _y Mn _1-y ] O ₂ (provided that 0.6
6 ≦ x ≦ 1.0 and 0 <y ≦ 0.18).

Further, the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention provides a method for producing a manganese compound raw material in which primary particles are aggregated to form spherical or elliptical secondary particles.
A sodium-lithium-manganese composite oxide is synthesized by mixing with a sodium compound and a lithium compound so as not to lose its shape, and has the formula Na _x [Li _y Mn _1-y ] O ₂
(However, 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.1
The sodium-lithium-manganese composite oxide represented by 8) is used as a precursor, and the precursor is treated in a solution or a molten salt containing lithium ions, whereby sodium ions contained in the precursor are converted into lithium ions. Ion exchange.

In the sodium-lithium-manganese composite oxide, the molar ratio of Na, Li and Mn is x: y: 1-y
(However, 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.1
8) A sodium compound, a lithium compound and a manganese compound are mixed so that
Heat-treated for 0 hour or more and quenched to room temperature or lower to obtain.

Alternatively, the molar ratio of Na, Li, and Mn is x: y: 1-y (provided that 0.66 ≦ x ≦ 1.0 and 0
<Y ≦ 0.18) Sodium compound and lithium compound are heated and melted or dissolved in a solvent, impregnated with a manganese compound, and heat-treated at a temperature of 600 ° C. or more for 10 hours or more, and at room temperature or less. Get quenched.

The sodium compound is sodium carbonate, sodium hydroxide or sodium nitrate, and the lithium compound is lithium carbonate, lithium hydroxide,
Preferably, the manganese compound is at least one selected from lithium hydroxide monohydrate and lithium nitrate, and the manganese compound is manganese dioxide, and the secondary particles have a spherical or elliptical spherical shape.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is Li _x [Li _y Mn _1-y ] O ₂ (0 ≦ x
≦ 1.0 and 0 <y ≦ 0.18), wherein the secondary particles of the lithium manganese composite oxide have a spherical or elliptical spherical shape.

A lithium manganese composite oxide having such powder characteristics is obtained as follows.

First, without passing through a pulverizing and mixing step in which the powder characteristics of a manganese compound whose secondary particles are spherical or elliptical are impaired, for example, an aqueous solution in which both a sodium compound and a lithium compound are dissolved is used. , By adding a manganese compound and evaporating it to dryness,
The molar ratio of Na, Li, and Mn is x: y: 1-y (however,
A mixture satisfying 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.18) is obtained, and the mixture is heat-treated and rapidly cooled to synthesize a precursor sodium-lithium-manganese composite oxide. .

Next, the sodium-lithium-manganese composite oxide can be obtained by stirring and heating in a solvent in which lithium halide is dissolved to exchange sodium ions for lithium ions.

The molar ratio of Na, Li and Mn x: y: 1-y
Can be obtained in the range of 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.18. If the range is out of this range, the layered lithium manganese oxide having no O2 structure can be obtained. Since many different compounds such as compounds are generated, the cycle characteristics of the battery deteriorate.

The manganese compound used in the present invention includes:
Manganese oxide, manganese hydroxide, manganese chloride, manganese carbonate, manganese nitrate, manganese sulfate, manganese acetate, and the like can be mentioned, and it is preferable that the secondary particles have powder characteristics such as spherical or elliptical spherical. But manganese dioxide is preferred.

As the sodium compound, sodium carbonate, sodium hydroxide, sodium nitrate and the like are preferable.

As the lithium compound, lithium carbonate,
Preferred are lithium hydroxide, lithium hydroxide monohydrate, lithium nitrate and the like.

The sodium compound and the lithium compound are mixed and heat-treated with the manganese compound to be in a molten state when the precursor sodium-lithium-manganese composite oxide is synthesized. Can be expected to proceed uniformly and quickly. As a result, even after ion exchange of the precursor, a lithium manganese composite oxide having a uniform composition can be obtained without impairing the powder characteristics of the manganese compound raw material.

By setting the temperature at the time of the heat treatment to 600 ° C. or higher, an O 2 -type layered composite oxide can be obtained without generating a different phase.

By using the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, a secondary battery having moldability and filling properties can be assembled while maintaining high initial capacity and cycle characteristics.

[0036]

Hereinafter, examples of the present invention will be described in detail along with comparative examples.

Example 1 Commercially available sodium hydroxide, lithium hydroxide monohydrate and spherical manganese dioxide were converted to Na,
After weighing so that the molar ratio of Li and Mn is 0.67: 0.17: 0.83, the solution is put into pure water in an amount in which sodium hydroxide and lithium hydroxide monohydrate are completely dissolved. The mixture was stirred while heating to evaporate water to obtain a dry powder.

This dried powder is heated at 800 ° C. in an oxygen stream.
After firing for 20 hours, the fired product was quickly taken out of the furnace and rapidly cooled.

The obtained fired product was subjected to composition analysis using an inductively coupled plasma atomic spectrometer (ICP). As a result, Na: Li: Mn = 0.67: 0.17: 0.83
And a result consistent with the charged composition was obtained. Further, the powder was analyzed by powder X-ray diffraction using Kα radiation of Cu. As a result, it was confirmed that the crystal had a hexagonal layered structure similar to β-Na _0.7 MnO ₂ .

This sodium-lithium-manganese composite oxide was put into hexanol in which lithium bromide was dissolved at a concentration of 1 M, and heated and stirred at 180 ° C. for 8 hours.
The resulting slurry was filtered. The solid remaining on the filter paper was washed with methanol and dried at 80 ° C. to obtain a positive electrode active material.

When the composition of the obtained positive electrode active material was analyzed using an inductively coupled plasma atomic spectrometer (ICP), Na: Li: Mn = 0.01: 0.50: 0.4.
9, indicating that Na was almost ion-exchanged to Li. Furthermore, when the powder X-ray diffraction pattern using Kα ray of Cu was analyzed by Rietveld analysis,
Li _0.70 [L of O2 type layered structure having space group P3ml
i _0.17 Mn _0.83 ] O ₂ pattern was very good.

The tap density of the obtained positive electrode active material was 1.70 g / cm ³ .

Using the obtained active material, the three-electrode cell shown in FIG. 1 was prepared as follows, and the charge / discharge capacity was measured.

To 87% by mass of the active material powder, 5% by mass of acetylene black and PVDF (polyvinylidene fluoride) 8
% By mass, and NMP (n-methylpyrrolidone) was added to form a paste. This was applied to an aluminum foil having a thickness of 20 μm so that the mass of the active material after drying was 0.02 g / cm ² , and vacuum dried at 120 ° C.
And a positive electrode 1 was punched out. In a glove box in an Ar atmosphere in which the dew point is controlled at −80 ° C., the positive electrode 1 and a counter electrode 3 and a reference electrode 2 made to the same dimensions as the positive electrode 1 using lithium metal in a glass cell 5. ,
Electrolyte solution 4 using an equimolar mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt was arranged to produce a three-electrode cell.

A charge / discharge test was performed at a current density of 0.06 mA / cm ² and a cutoff voltage of 4.6 V to 2.0 V.

The obtained first cycle discharge capacity (initial capacity) was 125 mAh / g. The ratio of the discharge capacity at the 20th cycle to the initial capacity (capacity maintenance ratio) was 7%.
0.0%.

(Example 2) Sodium hydroxide, lithium hydroxide monohydrate and spherical manganese dioxide were converted to Na, Li,
A positive electrode active material was synthesized in the same manner as in Example 1, except that the Mn molar ratio was weighed so as to be 0.67: 0.06: 0.94.

The tap density of the obtained positive electrode active material was 1.6.
It was 5 g / cm ³ .

Further, using the obtained positive electrode active material, a three-electrode cell was prepared in the same manner as in Example 1, and a charge / discharge test was performed.

The obtained first cycle discharge capacity (initial capacity) was 150 mAh / g. The ratio of the discharge capacity at the 20th cycle to the initial capacity (capacity maintenance rate) is 6
8%.

Comparative Example 1 Commercially available sodium carbonate, lithium carbonate, and spherical manganese dioxide were weighed so that the molar ratio of Na, Li, and Mn was 0.67: 0.17: 0.83. Was wet-mixed with ethanol using a ball mill for 15 hours. The obtained slurry mixture was dried in an atmosphere at 85 ° C. for 3 hours to obtain a mixed dry powder. This mixed dry powder is placed in an oxygen stream at 800 ° C. for 2 hours.
After firing for 0 hours, the fired product was quickly taken out of the furnace and rapidly cooled.

When the obtained fired product was subjected to composition analysis using an inductively coupled plasma atomic spectrometer (ICP), Na: Li: Mn = 0.67: 0.17: 0.83.
And a result consistent with the charged composition was obtained. Further, when analyzed by powder X-ray diffraction using Cu Kα ray, it was confirmed that the crystal structure had a hexagonal layered structure similar to β-Na _0.7 MnO ₂ .

This sodium-lithium-manganese composite oxide was put into hexanol in which lithium bromide was dissolved at a concentration of 1 M, and the mixture was heated and stirred at 180 ° C. for 8 hours, and the obtained slurry was filtered. The solid remaining on the filter paper was washed with methanol and dried at 80 ° C. to obtain a positive electrode active material.

When the composition of the obtained positive electrode active material was analyzed using an inductively coupled plasma atomic spectrometer (ICP), Na: Li: Mn = 0.01: 0.50: 0.4.
9, indicating that Na was almost ion-exchanged to Li. Furthermore, when the powder X-ray diffraction pattern using Kα ray of Cu was analyzed by Rietveld analysis,
Li _0.70 [L of O2 type layered structure having space group P3ml
i _0.17 Mn _0.83 ] O ₂ pattern was very good.

The tap density of the obtained positive electrode active material was 0.50 g / cm ³ .

Further, a three-electrode cell was prepared in the same manner as in Example 1 using the obtained positive electrode active material, and a charge / discharge test was performed.

The obtained first cycle discharge capacity (initial capacity) was 160 mAh / g. The ratio of the discharge capacity at the 20th cycle to the initial capacity (capacity maintenance ratio) was 7%.
It was 0%.

(Comparative Example 2) Commercially available lithium hydroxide and spherical manganese dioxide were weighed so that the molar ratio of Li and Mn was 1: 2, and then these compounds were contained in secondary particles of manganese dioxide. The mixture was mixed with such a force that the spherical or elliptical spherical shape did not collapse, and fired at 800 ° C. for 10 hours to obtain a positive electrode active material.

When the composition of the obtained positive electrode active material was analyzed using an inductively coupled plasma atomic spectrometer (ICP), Li: Mn = 1: 2, and a result consistent with the charged composition was obtained. Was. Further, when the powder was analyzed by powder X-ray diffraction using Cu Kα ray, it was confirmed that the powder had a spinel structure of LiMn ₂ O ₄ .

The tap density of the obtained positive electrode active material was 1.72 g / cm ³ .

Further, using the obtained positive electrode active material, a three-electrode cell was prepared in the same manner as in Example 1, and a charge / discharge test was performed.

The obtained first cycle discharge capacity (initial capacity) was 220 mAh / g. The ratio of the discharge capacity at the 20th cycle to the initial capacity (capacity retention ratio) is 2
7%.

(Evaluation) As shown in Comparative Example 1, the O2 type lithium manganese composite oxide synthesized by finely pulverizing and mixing the raw materials certainly has a relatively high initial characteristic of 100 mAh / g or more and a good cycle. You can get the characteristics,
The density of the active material becomes low, and an electrode having a high capacity per volume cannot be obtained.

As shown in Comparative Example 2, the spinel-type lithium manganese composite oxide composed of spherical or elliptical secondary particles can obtain a relatively high density and a large initial capacity. Very poor cycle characteristics.

On the other hand, as in Examples 1 and 2, the O2 type lithium manganese composite oxide of the present invention composed of spherical or oval spherical secondary particles has a thickness of 100 m.
A relatively high initial capacity of Ah / g or more and good cycle characteristics can be simultaneously obtained.

[0066]

As described above, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention maintains the high cycle characteristics of a non-aqueous electrolyte secondary battery while maintaining the moldability and filling properties of the positive electrode. Thus, a secondary battery having a large initial capacity per unit volume can be provided.

[Brief description of the drawings]

FIG. 1 is a side view showing a three-electrode cell according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode (evaluation electrode) 2 Reference electrode (Li) 3 Counter electrode (Li) 4 Electrolyte 5 Glass cell

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G048 AA04 AB01 AB02 AB05 AC06 AD06 AE05 5H029 AJ03 AK03 AL12 AM03 AM05 AM07 CJ02 CJ08 CJ15 CJ23 DJ16 DJ17 HJ00 HJ02 HJ13 HJ14 5H050 AA08 BA15 CA09 CB12 FA17 GA19 GA02 HA13 HA14 HA20

Claims (9)

[Claims] 1. A spherical or elliptical secondary particle formed by agglomeration of primary particles of an O2 type layered lithium manganese composite oxide in which a part of Mn is substituted by Li. Positive electrode active material for non-aqueous electrolyte secondary batteries. 2. An O2-type layered lithium manganese composite oxide in which a part of Mn is replaced with Li, a manganese compound raw material comprising spherical or elliptical secondary particles formed by agglomeration of primary particles is formed. A lithium-manganese composite obtained by mixing a sodium compound and a lithium compound to synthesize a sodium-lithium-manganese composite oxide and exchanging sodium ions contained in the composite oxide into lithium ions so as not to destroy A positive electrode active material for a non-aqueous electrolyte secondary battery, which is an oxide. 3. An O2-type layered structure in which a crystal structure is represented by a space group P3ml, two manganese oxide layers are present in a unit cell, and lithium ions are present at octahedral positions of the oxide ions. _x [Li _y Mn _1-y ] O ₂ (provided that 0.
The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode active material is represented by the following formula: 66 ≦ x ≦ 1.0 and 0 <y ≦ 0.18). 4. A manganese compound raw material comprising spherical or elliptical secondary particles formed by aggregating primary particles,
The compound is synthesized by mixing with a sodium compound and a lithium compound so as not to lose its shape, and has the formula Na _x [Li _y Mn _1-y ] O
₂ (However, 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.1
The sodium-lithium-manganese composite oxide represented by 8) is used as a precursor, and the precursor is treated in a solution or a molten salt containing lithium ions, whereby sodium ions contained in the precursor are converted into lithium ions. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, characterized by performing ion exchange. 5. Molar ratio of Na, Li, Mn is x: y: 1.
−y (where 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.
18), a sodium compound, a lithium compound and a manganese compound are mixed, and the mixture is heated at a temperature of
Heat treatment for 0 hour or more, and quenching to room temperature or less,
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the sodium-lithium-manganese composite oxide is obtained. 6. The molar ratio of Na, Li, and Mn is x: y: 1.
−y (where 0.66 ≦ x ≦ 1.0 and 0 <y ≦ 0.
18) so that the sodium compound and the lithium compound are heated and melted or dissolved in a solvent, impregnated with a manganese compound, heat-treated at a temperature of 600 ° C. or more for 10 hours or more, and rapidly cooled to a room temperature or less. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the sodium-lithium-manganese composite oxide is obtained. 7. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the sodium compound is sodium carbonate, sodium hydroxide or sodium nitrate. 8. The method according to claim 1, wherein the lithium compound is lithium carbonate,
7. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the method is at least one selected from lithium hydroxide, lithium hydroxide monohydrate and lithium nitrate. 9. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the manganese compound is manganese dioxide.