JP2000340226A - Lithium manganese composite oxide particle and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a primary particle and a secondary particle as active material for a positive electrode of a lithium ion secondary battery and a manufacturing method thereof effective for improving battery performance such as (initial) battery capacity and charge and discharge cycle characteristics or the like. SOLUTION: This lithium manganese composite oxide particle contains lithium manganese composite oxide expressed by the formula: LiMn2-xMxO4 (M is at least one of elements selected from Cr, Ni, Fe, Co, Mg, and Li, 0<x<=0.4). An amount (W1) of M contained in the lithium manganese composite oxide for forming a surface layer is more than an amount (W2) of M contained in the lithium manganese composite oxide for forming an inner layer in a primary particle of the lithium manganese composite oxide. A secondary particle of the lithium manganese composite oxide is formed by integrally forming a continuous phase with the surface layer of the primary particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to primary and secondary particles of a lithium manganese composite oxide, a method for producing the lithium manganese composite oxide secondary particles, and a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, as a portable device driven by a battery has become smaller and lighter, a lithium ion secondary battery has been put to practical use as a battery mounted as a power source in the portable device. Lithium ion secondary batteries are composed of a positive electrode using a lithium-containing compound as an active material, a negative electrode using a carbon material capable of occluding and releasing lithium ions as an active material, and a separator including a non-aqueous electrolyte, or a solid electrolyte. ing.

The lithium-containing compounds used for the positive electrode active material include LiCoO ₂ , LiNiO ₂ and LiMn.
₂ O _{4 and the} like are being studied. Among them, LiMn ₂ O ₄
Since the material cost is lower than that of LiCoO ₂ or LiNiO ₂ , it is expected to be used not only for small devices but also as a positive electrode active material for large batteries for electric vehicles. For example, Japanese Patent Application Laid-Open No. H10-255804 describes that 700 to 5000
(2) A lithium secondary battery using hollow lithium manganese composite oxide secondary particles composed of lithium manganese composite oxide single crystal primary particles as a positive electrode active material is disclosed.

On the other hand, when a lithium manganese composite oxide is used as a positive electrode active material, there is a problem that charge / discharge cycle characteristics are not sufficient. This is a phenomenon in which manganese dissolves out of the lithium manganese composite oxide into the electrolyte when the charge and discharge are repeated, thereby reducing the battery capacity, and is particularly remarkable at high temperatures. In order to solve this problem, a method of stabilizing the spinel structure by substituting a part of Mn with another element has been proposed (for example, Masao Yoshio: Lecture at the 66th Annual Meeting of the Institute of Electrical Chemistry, Japan). Abstracts, p. 273 (1999)).

[0005]

However, a lithium ion secondary battery using primary or secondary particles of a lithium manganese composite oxide obtained by a conventional method as a positive electrode active material has a charge / discharge cycle. Although the characteristics are improved, there is a problem that the (initial) battery capacity is greatly reduced.

Accordingly, a first object of the present invention is to provide lithium manganese composite oxide primary particles useful as a material for an active material for a positive electrode of a lithium ion secondary battery.
A second object of the present invention is to provide a lithium-manganese composite oxide which is used as a positive electrode active material of a lithium ion secondary battery and is effective for improving battery performance such as (initial) battery capacity and charge / discharge cycle characteristics. It is to provide secondary particles. Further, a third object of the present invention is to provide a method suitable for producing the lithium manganese composite oxide secondary particles. Further, a fourth object of the present invention is to provide an (initial)
It is to provide a secondary battery having a high battery capacity and excellent charge / discharge cycle characteristics.

[0007]

Means for Solving the Problems In order to improve the charge / discharge cycle characteristics without impairing the (initial) battery capacity of a lithium ion secondary battery, the present inventors have proposed a lithium ion secondary battery as a positive electrode active material. The lithium manganese composite oxide used has been studied diligently. As a result, the particles of the lithium-manganese composite oxide have a two-layer structure having an inner core portion and a surface layer covering the inner core portion, and the surface layer has more elements stabilizing the spinel structure than the inner core portion. It has been found that primary particles having a structure including the above are effective in solving the above-mentioned problem. Furthermore, they found that secondary particles composed of primary particles having a two-layer structure and having a specific structure were effective, and completed the present invention. That is, when used as a positive electrode active material, only the surface layer in contact with the electrolytic solution is Cr, N
The spinel structure in the surface layer portion is stabilized by being formed of a lithium manganese composite oxide having a composition with a high content of at least one selected from i, Fe, Co, Mg and Li. The primary particles of the lithium-manganese composite oxide having such a two-layer structure and the secondary particles composed of the primary particles are effective in improving the (initial) battery capacity and charge / discharge cycle characteristics of a lithium ion secondary battery. I learned.

That is, the present invention has been made based on the above-mentioned findings,
Formula (a): LiMn _2-x M _x O ₄ (a) (where M is at least one selected from Cr, Ni, Fe, Co, Mg and Li, and x is 0 <x ≦
0.4) and are particles having an inner core portion and a surface layer covering the outer surface of the inner core portion, wherein the lithium manganese composite oxide constituting the surface layer portion is a particle. It is intended to provide lithium manganese composite oxide primary particles, characterized in that the content of the element M therein is larger than the content of the element M of the lithium manganese composite oxide constituting the inner core.

Further, the present invention provides a lithium manganese composite oxide in which the primary particles of the lithium manganese composite oxide assemble and are continuously bonded to each other, and a surface layer of each primary particle forms a continuous phase integrally. It provides secondary particles.

Further, the present invention provides a positive electrode active material for a lithium ion secondary battery comprising the above-mentioned lithium manganese composite oxide secondary particles and a lithium ion secondary battery having a positive electrode containing the positive electrode active material. It is.

Further, the present invention provides a method for producing the secondary particles of lithium manganese composite oxide as described above, wherein Li element, Mn element, Cr, Ni, Fe, Co, Mg
Solution A containing at least one element M selected from Li and Li is sprayed and pyrolyzed to produce lithium manganese composite oxide particles, and then Li element, Mn element, and Cr, Ni, Fe, Co, Mg Spraying and pyrolyzing a suspension obtained by suspending the lithium composite oxide particles in a solution B containing at least one element M selected from Li and Li; The present invention provides a method for producing lithium manganese composite oxide secondary particles in which the number of moles of the Li element, the Mn element, and the element M satisfy the following formula (b). [(M) _A / {(Li) _A + (Mn) _A + (M) _A }] <[(M) _B / {(Li) _B + (Mn) _B + (M) _B }] (b) Where (Li) _A : mole number of Li element in solution A (Mn) _A : mole number of Mn element in solution A (M) _A : mole number of element M in solution A (Li) _B : solution The number of moles of the Li element in _B (Mn) _B : the number of moles of the Mn element in the solution B (M) _B : the number of moles of the element M in the solution B.

Hereinafter, the primary and secondary particles of the lithium manganese composite oxide of the present invention, the method for producing the lithium manganese composite oxide secondary particles, and the lithium ion secondary battery will be described.

The primary particles of the lithium manganese composite oxide of the present invention are composed of the lithium composite oxide represented by the formula (a). In the formula (a), M is Cr, N
i, at least one element selected from Fe, Co, Mg and Li. The lithium manganese composite oxide used in the present invention may contain only one of these elements, or may contain two or more of these elements. In the present invention, among these elements, a lithium manganese composite oxide containing Cr and Fe is preferable from the viewpoint of improvement in charge / discharge cycle characteristics, and a lithium manganese composite oxide containing Cr is particularly preferable.

The lithium manganese composite oxide primary particles of the present invention (hereinafter referred to as “primary particles of the present invention”)
It is a particle having an inner core portion and a surface layer portion covering the outside of the inner core portion. The inner core portion and the surface layer portion are both composed of the lithium manganese composite oxide represented by the formula (a), and the content of the element M in the lithium manganese composite oxide constituting the surface layer portion constitutes the inner core portion. It is formed so as to be larger than the content of the element M of the lithium manganese composite oxide. That is, the molar ratio of Li / Mn / element Mn in the lithium manganese composite oxide constituting the surface layer portion was set to 1 /
Assuming that the molar ratio of Li / Mn / element Mn in the lithium manganese composite oxide constituting the inner core portion is 1 / (2-xi) / xi with respect to (2-xs) / xs, xs> xi
It is formed so that For example, a substituted lithium manganese composite oxide containing Cr as the element M: LiMn
_{When the} primary particles are composed of _2-x Cr _x O ₄ , it means that the surface layer has a composition of LiMn _1.6 Cr _0.4 O ₄ , whereas the inner core has a composition of LiMn _1.9 Cr _0.1 O ₄ .

In the primary particles of the present invention, the content of the element M in the surface layer portion is larger than the content of the element M in the inner core portion, that is, xs> xi, whereby lithium manganese in the surface layer portion of the primary particles is obtained. The spinel crystal structure of the composite oxide can be further stabilized. Therefore, when the primary particles are used as a positive electrode active material, the elution of Mn from the particle surface can be suppressed by the contacting electrolyte, and a decrease in the battery capacity of the lithium ion battery can be suppressed, and at the same time, the charge can be suppressed. It is considered that the cycle characteristics of the discharge can be improved.

In the lithium manganese composite oxide constituting the primary particles of the present invention, x representing the molar ratio of the element M to Li in the formula (a) is 0 <x ≦ 0.
4 and preferably in the range of 0.1 ≦ x ≦ 0.3. When x exceeds 0.4, the element M that substitutes for the spinel crystal site is too large, and when used as a positive electrode active material of a lithium ion secondary battery, the diffusion path of lithium ions is hindered, and the battery capacity decreases. There is a possibility that. Further, xs and xi are preferably in the ranges of 0 <xs ≦ 0.4 and 0 ≦ xi <0.4, respectively, and particularly, 0.1 <xs ≦ 0.3 and 0 ≦ xi <0.1. It is preferably within the range.

In the primary particles of the present invention, the inner core is made of a single crystal of a lithium manganese composite oxide, and the surface layer is made of a crystal of a lithium manganese composite oxide epitaxially grown on the inner core. The use as a positive electrode active material is preferable in that a reduction in battery capacity can be further suppressed and a lithium ion battery having excellent battery performance can be obtained. This is generally because the diffusion path of lithium ions in the spinel crystal is 8a site → 1
6c site → 8a site, and if this diffusion path is interrupted by crystal defects such as grain boundaries, the diffusion coefficient of lithium ions is reduced and the battery capacity is degraded. Therefore, the inner core of the primary particles of the lithium manganese composite oxide particles is a single crystal, and the surface layer for stabilizing the spinel is also epitaxially grown with crystal consistency with the inner core to form one single particle for the entire primary particles. It is considered that a decrease in battery capacity can be suppressed in the crystalline state.

In the primary particles having a two-layer structure of the present invention, the thickness of the surface layer is preferably in the range of 10 to 1000 °, particularly preferably in the range of 20 to 50 °. When the thickness of the surface layer is too thin, when used as a positive electrode active material of a lithium ion secondary battery, manganese is easily eluted from the particle surface, and the charge / discharge cycle characteristics are not improved. Battery capacity decreases.

The primary particles of the present invention have a particle size of 0.1.
The range is preferably from 0.1 to 10 μm, particularly preferably from 0.1 to 5 μm.
The range of m is preferred. The smaller the particle size, the smaller the diffusion distance of lithium ions, which is suitable for charging and discharging in a short time.However, since the specific surface area increases, the activity of the powder increases, causing a problem in safety. There is a risk. Also, when the particle diameter is large, there is a possibility that charging and discharging in a short time may be hindered.

The present invention also provides a lithium manganese composite oxide secondary particle in which the primary particles of the present invention are aggregated and continuously bonded, and the surface layer of each primary particle forms a continuous phase integrally. (Hereinafter referred to as “secondary particles of the present invention”). The secondary particles 7 of the present invention, for example, FIG.
As shown in the schematic cross-sectional view of FIG.
1b, 1c,... Are aggregated and continuously bonded, and the surface layers 2a, 2b, 2c... Of the primary particles 1a, 1b, 1c. Primary particles 1a,
The inner core portions 4a, 4b, 4c,... Of 1b, 1c are included in the continuous phase 3 and have a structure having a particle diameter larger than the primary particles. The continuous phase 3 is continuously formed not only outside the secondary particles but also inside the secondary particles, and includes the inner core portions 4a, 4b, 4c....

The secondary particles of the present invention are shown in FIGS. 1 and 2 as long as the primary particles are aggregated, the surface layer of the primary particles forms a continuous phase, and has a larger particle diameter than the primary particles. It is not limited to the structure. In particular, as shown in FIG. 1 as an example, there are no primary particles to be bonded on the outer surface or inside, and porous secondary particles having pores 5 formed therein, and as shown in FIG. The secondary particles having the structure in which the portion 6 is formed are preferable in that the electrolyte easily enters the inside of the secondary particles and the battery capacity is improved.

The secondary particles of the present invention are shown in FIGS.
Are not limited to those having a substantially spherical outer shape, and for example, may have a shape such that hollow particles are crushed. In particular, when the active material is applied on the current collector, a material having a substantially spherical outer shape is preferable from the viewpoint of filling properties and applicability.

The secondary particles of the present invention have a particle size of 0.1 to 5
A range of 0 μm is preferred, and a range of 5 to 20 μm is particularly preferred. If the particle size is smaller than 0.1 μm, the activity becomes too large, which causes a problem in safety. In addition, in the lithium ion secondary battery, the active material for the positive electrode is used by being coated on the current collector to a thickness of 100 to 200 μm, and therefore, if the particle diameter of the secondary particles is too large, the applicability may be deteriorated. is there.

The production of the secondary particles of the present invention is not particularly limited as long as the primary particles of the two-layer structure can be aggregated to form the secondary particles of the structure. Is also good. In particular, in the present invention, as the method for producing the secondary particles, (1) Li element, Mn element,
Spraying and thermally decomposing a solution A containing at least one element M selected from Cr, Ni, Fe, Co, Mg and Li to produce lithium manganese composite oxide particles; and (2) Li element , Mn element, and C
spraying and pyrolyzing a suspension obtained by suspending the lithium composite oxide particles in a solution B containing at least one element M selected from r, Ni, Fe, Co, Mg and Li; A solution A used in the step (1),
The method of adjusting the number of moles of the Li element, the Mn element and the element M in the solution B used in the step (2) so as to satisfy the following formula (b) (hereinafter referred to as “the method of the present invention”) is mentioned. Can be [(M) _A / {(Li) _A + (Mn) _A + (M) _A }] <[(M) _B / {(Li) _B + (Mn) _B + (M) _B }] (b) Where (Li) _A : mole number of Li element in solution A (Mn) _A : mole number of Mn element in solution A (M) _A : mole number of element M in solution A (Li) _B : solution Molar number of Li element in _B (Mn) _B : mole number of Mn element in solution B (M) _B : mole number of element M in solution B

In the method of the present invention, step (1) is a step of producing particles corresponding to the inner core of the primary particles of the present invention. That is, the molar ratio of Li / Mn / M is 1 / (2
A solution A was prepared by mixing a Li compound, a Mn compound and a compound containing the element M at a ratio of -xi) / xi, and this solution A was sprayed and thermally decomposed to obtain the above formula (a). This is a step of producing primary particles and / or secondary particles of a single-layer structure composed of a lithium manganese composite oxide in which the molar ratio of the element M is x = xi. The particles correspond to particles constituting the inner core.

The solution A can be prepared by any method as long as the Li compound, the Mn compound and the compound containing the element M are charged into the solvent at the above-mentioned ratio and stirred to be uniform. Therefore, you may do so. Examples of the solvent used include water and alcohol. Among these, water is preferred from the viewpoint of safety, cost, and the like.
It is preferable that the total concentration of the Li compound, the Mn compound, and the compound containing the element M in the solution A is adjusted to a range of 0.1 to 1.0 mol / l.

The spraying and thermal decomposition of the solution A can be performed, for example, by spraying the solution into a tubular pyrolysis furnace maintained at a predetermined temperature.

Next, step (2) is a step of forming a surface layer on the particles obtained in step (1). That is, Li
A solution B containing a Li compound, a Mn compound and a compound containing the element M is prepared at a ratio such that the molar ratio of / Mn / M is 1 / (2-xs) / xs. The particles obtained in (1) are mixed and suspended to prepare a suspension. Next, the suspension is sprayed and thermally decomposed, and in the above formula (a), the surface layer portion of the lithium manganese composite oxide in which the molar ratio of the element M is x = xs corresponds to the inner core portion. This is a step of forming on the surface of the particles having a single layer structure.

The preparation of the solution B and the treatment of spraying / pyrolysis can be performed in the same manner as in the above step (1). When the particles obtained in the step (1) are 10 to 200 g / l
The solution B is adjusted so as to be suspended to a degree.

In the method of the present invention, step (1)
The temperature of spraying / pyrolysis in (2) is 600 to
A range of 900 ° C is preferable, and a range of 700 to 800 ° C is particularly preferable. If the temperature of the spraying / pyrolysis is lower than 600 ° C., the generated oxide may be decomposed into two phases of LiMn ₂ O ₄ + Mn ₂ O ₃ and a lithium manganese composite oxide may not be formed. If it exceeds 300, the structure will be deficient in oxygen, and the battery capacity may be reduced.

Further, in the method of the present invention, when heat treatment is performed after the spraying / pyrolysis in the steps (1) and (2), primary particles having good crystallinity are easily obtained. The temperature of this heat treatment is 60 for the same reason as the temperature of spraying / pyrolysis.
A range from 0 to 900C is preferred.

The primary particles and secondary particles of the present invention are preferable as a positive electrode active material of a lithium ion secondary battery. In particular, the positive electrode active material for a lithium ion secondary battery comprising the secondary particles of the present invention is effective for obtaining a lithium ion secondary battery having a high battery capacity and excellent charge / discharge cycle characteristics.

The lithium ion secondary battery having a positive electrode containing the secondary particles of the present invention as an active material (hereinafter referred to as “secondary battery of the present invention”) is a positive electrode containing the secondary particles of the present invention as an active material. , A negative electrode, and a non-aqueous electrolyte. The positive electrode of this secondary battery contains the active material comprising the secondary particles of the present invention and other components used as a positive electrode material of this type of lithium ion secondary battery. For example, conductive conjugated polymer substances such as polyacetylene, polyparaphenylene, and polypyrrole; conductive materials such as acetylene black, carbon black, and graphite:
Polytetrafluoroethylene, ethylene propylene
It may contain a binder such as a diene copolymer or styrene / butadiene rubber.

The negative electrode of the secondary battery of the present invention is not particularly limited, and lithium, a lithium alloy, or another compound having a property of inserting and extracting lithium ions can be used. What is used as a negative electrode agent of a battery can be used. As the lithium alloy, for example, LiAl, LiPb, Li
Sn, LiBi and the like can be mentioned. Examples of the compound having the property of inserting and extracting lithium ions include conductive polymers such as polyacetal, polyacetylene, and polypyrrole doped with lithium ions, and carbon materials such as graphite. Further, by adding a binder such as polyethylene or polytetrafluoroethylene, and forming a pressure roll into a shape suitable for forming a negative electrode, for example, a sheet or a plate, and then performing a reduction treatment using lithium metal as a counter electrode, it is easy. A high performance negative electrode can be obtained.

The non-aqueous electrolyte may be any as long as it can dissolve the lithium salt, and is particularly preferably an aprotic organic solvent having a large dielectric constant. As the organic solvent, for example,
Propylene carbonate, ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, 4-methyl-dioxolan, acetonitrile, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like can be mentioned. These solvents can be used alone or in a suitable mixture. As the non-aqueous electrolyte, lithium salts which generate stable anions, such as lithium perchlorate, lithium borofluoride, lithium hexachloride antimonate, and lithium hexafluoroantimonate, are suitable.

A separator such as a nonwoven fabric made of synthetic fiber or glass fiber, a woven fabric, a polyolefin-based porous membrane, or a nonwoven fabric made of polytetrafluoroethylene is provided between the positive electrode and the negative electrode. In addition, a current collector can be used as in the case of a conventional battery. As the negative electrode current collector, a conductor which is electrochemically inert to an electrode, an electrolytic solution, or the like, for example, a metal such as copper, nickel, titanium, and stainless steel can be used in the form of a plate, a foil, or a rod.

The secondary battery of the present invention uses the above-mentioned battery components such as the separator, current collector, gasket, sealing plate, and case and the specific positive electrode of the present invention, and is in a cylindrical, square or button type according to a conventional method. And the like.

[0038]

The present invention will be described in more detail with reference to the following examples and comparative examples.

Examples 1 to 13 and Comparative Examples 1 to 5 Lithium nitrate and manganese acetate were used as compounds containing the metal elements Li and Mn constituting the lithium manganese composite oxide represented by the formula (a). As a compound containing the element M, a nitrate of the element M shown in Table 1 was used. These compounds were converted to a molar ratio of Li / Mn / M: 1 / (2-x
i) / xi is the value shown in Table 1 (molar ratio x of M in the lithium manganese composite oxide constituting the inner core)
After weighing to obtain i), the resultant was mixed with water and dissolved to prepare an aqueous solution (A). Next, the aqueous solution (A) is atomized by applying ultrasonic waves of 1.6 MHz using an ultrasonic vibrator, and the aqueous solution (A) in the atomized state is maintained at 750 ° C. by a carrier gas (air). Lithium nitrate, manganese acetate and the nitrate of the element M were supplied to the core tube and pyrolyzed to obtain lithium manganese composite oxide particles. The obtained lithium manganese composite oxide particles were placed in an alumina crucible and heat-treated at 750 ° C. for 1 to 24 hours.

Next, the obtained lithium manganese composite oxide particles were subjected to a Li / Mn / M molar ratio of 1 / (2-xs).
Lithium nitrate, manganese acetate and the nitrate of element M were weighed so that xs in / xs became the value shown in Table 1 (molar ratio xs of M in the lithium manganese composite oxide constituting the surface layer portion). It was suspended in an aqueous solution (B) prepared by mixing and dissolving to obtain a suspension. The suspension is atomized by applying ultrasonic waves of 1.6 MHz using an ultrasonic vibrator, and the atomized suspension is supplied to a furnace core tube maintained at 750 ° C. by a carrier gas (air). Then, lithium nitrate, manganese acetate and the nitrate of the element M were thermally decomposed to produce particles. Furthermore, the obtained particles are again
The powder was placed in an alumina crucible and heat-treated at 750 ° C. for 1 to 24 hours to obtain a powder composed of lithium manganese composite oxide secondary particles.

The obtained lithium manganese composite oxide secondary particles were observed with a scanning electron microscope to examine the morphology of the secondary particles, and the particle diameter of the primary particles constituting the secondary particles,
The particle diameter and particle shape of the secondary particles were examined. Further, when the powder composed of the lithium manganese composite oxide secondary particles was sliced with a microtome and the internal structure of the particles was analyzed with a transmission electron microscope, the concentration of the element M in the surface layer of the primary particles constituting the secondary particles was high. It was found that the material had a surface layer containing a large amount of the element M and an inner core containing a small amount of the element M.

Further, the lithium-manganese composite oxide particles were subjected to electron beam diffraction, and the crystallinity (single crystal or polycrystalline) was examined from the obtained diffraction pattern.

The charge / discharge test was performed according to the following method.
After the initial battery capacity and 20 cycles of charge and discharge
Was measured. Charge / discharge test The lithium-manganese composite oxide secondary particles
Of powder 80 parts by weight and carbon black 15 parts by weight
Of lithium metal as anode and electrolyte as electrolyte.
Equal volume mixture of Tylene carbonate / Dimethyl carbonate
LiPF for liquid₆Is dissolved at a rate of 1 mol / liter
Cell type lithium ion secondary
A battery was manufactured. About this lithium ion secondary battery
To measure the initial battery capacity and at a temperature of 50 ° C.
1.0 mA / cm ^Two, Charge end voltage
20 charge / discharge at 4.3 V and discharge end voltage 3.0 V
Battery cycle after 20 cycles.
The retention was measured. Table 1 shows the results.

[0044]

[Table 1]

[0045]

[Table 2]

In Table 1, Comparative Examples 1 and 2 are examples of lithium manganese composite oxide particles having a single-layer structure obtained by the preceding steps of preparing the aqueous solution (A), atomizing and heat-treating the aqueous solution (A). Comparative Examples 3 and 4 are examples of secondary particles in which the molar ratio xs of the element M in the lithium manganese composite oxide constituting the surface layer portion exceeds 0.4, and Comparative Example 5 has the molar ratio xs of the element M that is higher than 0.4. 0, that is, an example of the secondary particles in which the lithium manganese composite oxide constituting the surface layer portion does not contain the element M. From the results shown in Table 1, when the lithium manganese composite oxide secondary particles of the present invention are used as an active material for a positive electrode, a secondary battery having excellent initial battery capacity and improved charge / discharge cycle characteristics at high temperatures is obtained. We can see that we can do it.

[0047]

The primary particles of the lithium manganese composite oxide of the present invention are useful as a material for a positive electrode active material of a lithium ion secondary battery. Further, the lithium manganese composite oxide secondary particles of the present invention can be used as an active material for a positive electrode of a lithium ion secondary battery to improve battery performance such as (initial) battery capacity and charge / discharge cycle characteristics. Thus, a highly reliable lithium ion secondary battery can be obtained. Furthermore, according to the method of the present invention, the lithium manganese composite oxide secondary particles of the present invention can be produced with high efficiency. Furthermore, the lithium ion secondary battery of the present invention has a high (initial) battery capacity, excellent charge / discharge cycle characteristics, and high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a lithium manganese composite oxide secondary particle of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating another example of the lithium manganese composite oxide secondary particles of the present invention.

[Explanation of symbols]

 1a, 1b, 1c Primary particle 2a, 2b, 2c Surface layer 3 Continuous layer 4a, 4b, 4c Inner core 5 Hole 6 Hollow 7 Secondary particle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Kikuchi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in Technical Research Institute, Kawasaki Steel Co., Ltd. 4G048 AA04 AA05 AB01 AB04 AB06 AC06 AD03 AD04 AD07 AE07 AE08 5H003 AA02 AA04 BA00 BA01 BA03 BB05 BC01 BC05 BD00 BD02 5H014 AA01 BB00 BB01 CC01 CC07 EE10 HH00 5H029 AJ03 AJ05 AK03 AL06 AL12 AM03 AM04 AM05 AM07 CJ02 CJ28 DJ12 DJ16 DJ17 HJ02 HJ04

Claims (9)

[Claims] 1. Formula (a): LiMn _2-x M _x O ₄ (a) (where M is at least one selected from Cr, Ni, Fe, Co, Mg and Li, and x is 0 <x ≦
0.4) particles comprising a lithium manganese composite oxide represented by the formula (1) and having an inner core portion and a surface layer covering the outside of the inner core portion, wherein the lithium manganese composite oxide constituting the surface layer portion is Primary particles of a lithium manganese composite oxide, wherein the content of the element M in the element is greater than the content of the element M in the lithium manganese composite oxide constituting the inner core. 2. The lithium according to claim 1, wherein the inner core portion is made of a single crystal of a lithium manganese composite oxide, and the surface layer portion is made of a crystal of a lithium manganese composite oxide epitaxially grown on the inner core portion. Primary particles of manganese composite oxide. 3. The lithium manganese composite oxide primary particles according to claim 1, wherein the surface layer has a thickness of 10 to 1000 °. 4. The lithium manganese composite oxide primary particles according to any one of claims 1 to 3, wherein the primary particles assemble and bond continuously, and a surface layer of each primary particle integrally forms a continuous phase. Lithium manganese composite oxide secondary particles. 5. The lithium manganese composite oxide secondary particles according to claim 4, which has a porous or hollow particle structure. 6. The device according to claim 4, wherein the outer shape is substantially spherical.
2. The lithium manganese composite oxide secondary particles according to 1. above. 7. An active material for a positive electrode of a lithium ion secondary battery, comprising the lithium manganese composite oxide secondary particles according to claim 4. 8. A lithium ion secondary battery comprising a positive electrode comprising the lithium manganese composite oxide secondary particles according to claim 4 as an active material. 9. Li element, Mn element, Cr, N
i, Fe, Co, Mg and a solution A containing at least one element M selected from Li and Li are sprayed and thermally decomposed to produce lithium manganese composite oxide particles. Then, Li element, Mn element, and Cr, Ni, Fe, C
o, a step of spraying and thermally decomposing a suspension obtained by suspending the lithium composite oxide particles in a solution B containing at least one element M selected from Mg and Li, wherein the solutions A and A method for producing lithium manganese composite oxide secondary particles in which the number of moles of the Li element, the Mn element, and the element M in the solution B satisfies the following formula (b). [(M) _A / {(Li) _A + (Mn) _A + (M) _A }] <[(M) _B / {(Li) _B + (Mn) _B + (M) _B }] (b) Where (Li) _A : mole number of Li element in solution A (Mn) _A : mole number of Mn element in solution A (M) _A : mole number of element M in solution A (Li) _B : solution The number of moles of the Li element in _B (Mn) _B : the number of moles of the Mn element in the solution B (M) _B : the number of moles of the element M in the solution B.