JP2002063904A - Positive electrode active material and nonaqueous electrolyte battery as well as their manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material having both load characteristics almost equivalent to LiMn2O4 and capacity as high as LiMnO2. SOLUTION: A positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a nonaqueous electrolyte interposed between the positive and the negative electrodes are provided, and the positive electrode active material has LiMn2O4 on the surface of compound particles expressed in a formula LiMnO2 or LiMn1-yMyO2 (where, M is an element including at least one kind from Al, B, Co and Ni).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material and a non-aqueous electrolyte battery using a lithium manganese composite oxide, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of various electronic devices, research on a rechargeable secondary battery as a power source that can be used conveniently and economically for a long time has been advanced. As typical secondary batteries, lead storage batteries, alkaline storage batteries, lithium secondary batteries, and the like are known. In particular, lithium secondary batteries have advantages such as high output and high energy density. The above lithium secondary battery includes a positive electrode capable of reversibly inserting and removing lithium ions, a negative electrode, and a non-aqueous electrolyte.

In general, as a negative electrode active material, metallic lithium, a lithium alloy, a conductive polymer doped with lithium, a layered compound (such as a carbon material or a metal oxide) or a compound containing lithium and having a high conductivity is used. Molecules and layered compounds (such as carbon materials and metal oxides) are used.

As an electrolytic solution, a solution in which a lithium salt is dissolved in an aprotic organic solvent such as propylene carbonate is used.

On the other hand, a metal oxide, a metal sulfide, a polymer, or the like is used as the positive electrode active material.
Non-lithium-containing compounds such as S ₂ , MoS ₂ , NbSe ₂ and V ₂ O ₅ and complex oxides already containing lithium such as LiMO ₂ (M = Co, Ni, Mn, Fe, etc.) have been proposed. I have.

Further, a polymer film such as polypropylene is used as the separator. In this case, the separator must be as thin as possible in view of lithium ion conductivity and energy density. Usually, a separator of 50 μm or less is considered practical. A battery composed of the above-described positive electrode, negative electrode, and a separator and an electrolyte interposed therebetween can be used as a chargeable / dischargeable secondary battery.

[0007]

While the capacity of lithium secondary batteries has been increasing, the search for materials for cost reduction has also been actively pursued. Above all, cobalt oxide conventionally used for the positive electrode is more expensive than other oxides such as nickel, manganese, and iron, and it has been desired to substitute a relatively inexpensive metal oxide. In particular, it has been desired to use manganese oxide, one of the cheapest transition metals, for the positive electrode. Among such manganese oxides, the spinel type compound LiMn ₂ O ₄ is most famous, but the theoretical capacity of this compound is less than 150 mAh / g, which is less than 274 mAh / g of LiCoO ₂ . This is because Li of LiCoO _{2 has} the same number of atoms as the transition metal in the formula, whereas LiMn ₂ O ₄ has only half the number of Lis of the transition metal.

Therefore, as a candidate for a cathode oxide containing manganese, LiMnO ₂ having a theoretical capacity comparable to that of LiCoO ₂ has been actively studied. According to earlier research reports, high-temperature LiMnO ₂ and low-temperature LiMnO ₂ are reported. The former was first reported by WJ Johnston et al (J. Am. Chem. So
c., 78, 325 (1956)) and R. Hoppe, G. Brachtel and M. Jan
sen (Z. Anorg. Allg. Chemie, 417, 1 (1975)) has determined the structure. The latter (low temperature type LiMnO ₂ ) is described in T. Ohzuk
u, A.Ueda, and T.Hirai (Chem.Express, Vol7.No.3,193 (1
992)) first reported. Both have an orthorombic lattice and have a structure characterized by the space group Pmnm.

Further, although the theoretical capacity is about 300 mAh / g, the theoretical capacity is not reached by using the charge / discharge conditions employed in the current non-aqueous electrolyte battery. The latter is 200 mA
h / g. In the discharge capacity, initially,
The former is a value of 50 mAh / g or less (2.0 V ≧ V (Li /
Li ⁺ )), and the latter is 190 mAh / g (under the same conditions), which is described in the above literature.

However, these values are 100 μA / cm ²
These are reported values at the following current densities. For practical use, a capacity at a current density of 500 μA / cm ² or more is required. When used at such a high load current density, the discharge capacity of LiMnO ₂ is 40 mA each.
h / g and 120 mAh / g. It is considered that the reasons are as follows. First, both have a crystal structure similar to a layer structure, but the diffusion path of Li is zigzag, and L
Fast diffusion of i cannot be obtained. Second, high temperature type LiMnO ₂
Has good crystallinity and low electronic resistance due to impurity defects, but low-temperature LiMnO ₂ has high crystal resistance due to poor crystallinity. As a result, the latter shows a significant IR drop at high loads (= high current density).

Under such circumstances, there has been a demand for a positive electrode active material having load characteristics of about LiMn ₂ O ₄ and high capacity of about LiMnO ₂ .

The present invention has been proposed in view of the above-mentioned conventional circumstances, and has a positive electrode active material having a load characteristic of about LiMn ₂ O ₄ and a high capacity of about LiMnO ₂ , and its positive electrode active material. It is an object of the present invention to provide a non-aqueous electrolyte battery using a substance.

[0013]

Means for Solving the Problems The positive electrode active material of the present invention comprises:
General formula LiMnO ₂ or LiMn _{1- y My} O ₂ (M is Al,
It is an element containing at least one of B, Co and Ni. ), Wherein LiMn ₂ O ₄ is present on the surface of the compound particles.

The positive electrode active material according to the present invention as described above has a high capacity, a general formula LiMnO ₂ or LiMnO ₂
On the surface of the _1-y M _y O ₂ with a compound represented by particles, because LiMn ₂ O ₄ electron conductivity, or ion-exchange reaction is good is present, those having both a high capacity and load characteristics and Become.

Further, a nonaqueous electrolyte battery of the present invention comprises a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a nonaqueous electrolyte interposed between the positive electrode and the negative electrode. The positive electrode active material has the general formula LiMnO ₂ or LiM
_{n 1-y M y O 2} (M is Al, B, of Co or Ni, is an element comprising at least one.) that LiMn ₂ O ₄ is present on the surface of the compound particles represented by Features.

In the non-aqueous electrolyte battery according to the present invention as described above, the high capacity, general formula LiMnO ₂ or LiMnO ₂
On the surface of the Mn _1-y M _y O ₂ with a compound represented by particles, since the electronic conductivity or ion exchange reaction is used a positive electrode active material LiMn ₂ O ₄ is present is good, and high capacity The load characteristics are compatible.

Further, the method for producing a positive electrode active material of the present invention comprises:
A manganese ion solution is mixed with a general formula LiMnO ₂ serving as a base.
Or _{LiMn 1-y M y O 2} (M is Al, B, Co or Ni
Is an element containing at least one of them. After adding to the compound particles represented by (1) and heating, a positive electrode active material having LiMn ₂ O ₄ present on the surface of the compound particles is obtained.

In the method for producing a cathode active material according to the present invention as described above, the manganese ion solution is added to the parent compound particles represented by the general formula LiMnO ₂ or LiMn _{1- y My} O _2. By heating, on the surface of the compound particles represented by the general formula LiMnO ₂ or LiMn _{1- y My} O ₂ having a high capacity, LiMn ₂ O ₄ having good electron conductivity or ion exchange reaction is An existing positive electrode active material is obtained.

A method for manufacturing a non-aqueous electrolyte battery includes a non-aqueous electrolyte including a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. In the method for producing a water electrolyte battery, when synthesizing the positive electrode active material, a manganese ion solution is mixed with a general formula LiMnO ₂ or LiMn _{1- y My} O ₂ (M is Al,
It is an element containing at least one of B, Co and NNi. After adding to the compound particles represented by (1) and heating, a positive electrode active material having LiMn ₂ O ₄ present on the surface of the compound particles is obtained.

In the method for producing a nonaqueous electrolyte battery according to the present invention as described above, a manganese ion solution is added to a parent compound particle represented by the general formula LiMnO ₂ or LiMn _{1- y My} O ₂ . Then, by heating, the surface of the compound particles represented by the general formula LiMnO ₂ or LiMn _{1- y My} O ₂ having a high capacity is provided with LiMn ₂ O ₄ having good electron conductivity or ion exchange reaction. Is obtained. Then, in the method for producing a nonaqueous electrolyte battery according to the present invention using such a positive electrode active material, a nonaqueous electrolyte battery having both high capacity and load characteristics can be obtained.

[0021]

Embodiments of the present invention will be described below.

FIG. 1 shows a configuration example of a nonaqueous electrolyte battery to which the present invention is applied. This non-aqueous electrolyte battery 1 includes a negative electrode 2,
A negative electrode can 3 containing the negative electrode 2, a positive electrode 4, a positive electrode can 5 storing the positive electrode 4, a separator 6 disposed between the positive electrode 4 and the negative electrode 2, and an insulating gasket 7; The positive electrode can 5 is filled with a non-aqueous electrolyte.

The negative electrode 2 is made of, for example, a metal lithium foil serving as a negative electrode active material. When a material that can be doped and dedoped with lithium is used as the negative electrode active material, the negative electrode 2 is formed by forming a negative electrode active material layer containing the negative electrode active material on a negative electrode current collector. As the negative electrode current collector, for example, a nickel foil or the like is used.

As the negative electrode active material which can be doped and dedoped with lithium, lithium metal, a lithium alloy, a conductive polymer doped with lithium, and a layered compound (carbon material, metal oxide, etc.) are used.

As the binder contained in the negative electrode active material layer, a known resin material or the like usually used as a binder for the negative electrode active material layer of this type of nonaqueous electrolyte battery can be used.

The negative electrode can 3 houses the negative electrode 2 and serves as an external negative electrode of the nonaqueous electrolyte battery 1.

The positive electrode 4 is formed by forming a positive electrode active material layer containing a positive electrode active material on a positive electrode current collector. As the positive electrode current collector, for example, an aluminum foil or the like is used.

Here, in the present invention, as the positive electrode active material,
Low temperature type LiMnO ₂ particles or LiMn _{1- y My} O ₂ (M is A
It is an element containing at least one of l, B, Co and Ni. ) A particle whose surface is modified to LiMn ₂ O ₄ is used.

The present inventors have made intensive studies and found that LiMnO ₂
In the structure, the particle surface that most contributes to the electron conductivity is L
By reforming into iMn ₂ O ₄ , a positive electrode active material having both high load characteristics and high capacity has been realized.

Low temperature type LiMnO_TwoHas been previously reported
LiMnO_TwoHas the highest charge / discharge capacity among compounds
One. On the other hand, spinel manganese compounds that have been put into practical use
(LiMn _TwoO_Four) Is LiMnO in theoretical capacity_TwoOf 50
%, 60% in actual capacity (here, the volume of spinel manganese)
Amount 115 mAh / g, LiMnO_Two190m capacity
Ah / g. ). Such a difference in capacity
Despite the fact, LiMn is actually_TwoO_FourIs used
ing. The reason for this is that LiMnO_TwoHas low load characteristics,
This is because the actual capacity is significantly reduced in a high load environment.

Specifically, the low-temperature type LiMnO shown in FIG.
_TwoAnd the LiMn shown in FIG._TwoO_FourLoad characteristics
As is clear from the comparison with
Mn _TwoO_FourIs excellent. The reason is on the surface
Because there is a difference. That is, LiMn_TwoO_FourSo, on the surface
Good electron conductivity or good ion exchange
Characteristics are good. Therefore, if you have high capacity but load characteristics
Inferior to LiMnO_TwoThe surface of an electron conductive or ion
LiMn with good exchange reaction_TwoO_FourCan be reformed into
Preferably, the compound is LiMnO_TwoHigh capacity and LiM
n_TwoO_FourCharacteristics that combine the high load characteristics of
You. LiMn_1-yM_yO_TwoThe same applies to.

Here, LiMnO ₂ particles or LiMn _1-y
The weight of M _y O ₂ particles and Ma, LiMnO ₂ particles or L
iMn _1-y M y O ₂ when the weight of LiMn ₂ O ₄ present on the surface of the particles was Mb, LiMnO ₂ or LiMn _1-y
The weight ratio of M _y O ₂ and _{LiMn 2 O 4 (Mb / Ma} ) is 0
<Mb / Ma <0.20 is preferable.
When Mb / Ma is greater than 0.20, this is due to Li
This indicates that the ratio of Mn ₂ O ₄ is increased, and the high load characteristics are increased, but the capacity is decreased. Mb /
When Ma is 0.20, the capacity is almost equal to that of a standard lithium ion positive electrode using LiCoO ₂ , so that there is no advantage in terms of capacity.

Therefore, LiMnO ₂ or LiMn _1-y M _y
When the weight ratio (Mb / Ma) between O ₂ and LiMn ₂ O ₄ is 0 <
By setting the range of Mb / Ma <0.20, LiMnO
₂ or the ones combines good balance without impairing the high-load characteristics of LiMn _1-y M y O high capacity ₂ and LiMn ₂ O _4.

Thus, the chemical formula is LiMnO ₂ or L
In particles represented as _{iMn 1-y M y O 2} , by using the composite oxide particles surface modified to LiMn ₂ O ₄ positive electrode active material for lithium ion secondary batteries or lithium secondary batteries A non-aqueous electrolyte that does not deteriorate the charge / discharge capacity and has a small capacity deterioration even under a high load condition, as compared with a conventionally reported lithium ion secondary battery or lithium secondary battery using LiMnO ₂ as a positive electrode active material. A battery can be realized.

As the binder contained in the positive electrode active material layer, a known resin material or the like which is generally used as a binder for the positive electrode active material layer of this type of nonaqueous electrolyte battery can be used.

The positive electrode can 5 houses the positive electrode 4 and serves as an external positive electrode of the nonaqueous electrolyte battery 1.

The separator 6 separates the positive electrode 4 and the negative electrode 2 from each other, and can be made of a known material generally used as a separator of this type of non-aqueous electrolyte battery. A polymer film is used. In addition, the thickness of the separator needs to be as small as possible from the relationship between lithium ion conductivity and energy density. Specifically, the thickness of the separator is suitably, for example, 50 μm or less.

The insulating gasket 7 is integrated into the negative electrode can 3. The insulating gasket 7 is for preventing the nonaqueous electrolyte filled in the negative electrode can 3 and the positive electrode can 5 from leaking.

As the non-aqueous electrolyte, a solution in which an electrolyte is dissolved in an aprotic non-aqueous solvent is used.

Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyl lactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, -Methyl 1,3-dioxolan, methyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate and the like can be used. In particular, from the viewpoint of voltage stability, propylene carbonate,
It is preferable to use cyclic carbonates such as vinylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate. In addition, such a non-aqueous solvent may be used alone or as a mixture of two or more.

Examples of the electrolyte dissolved in the non-aqueous solvent include LiPF ₆ , LiClO ₄ , LiAsF ₆ ,
Lithium salts such as LiBF ₄ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ can be used. Among these lithium salts, LiPF ₆ and LiBF ₄ are preferably used.

As described above, in the nonaqueous electrolyte battery according to the present invention, LiMnO ₂ particles or LiMn _1-y having high capacity are provided.
The surface of M _y O ₂ particles, because of the use of positive electrode active material comprising reformed in LiMn ₂ O ₄ having excellent load characteristics, high capacity and excellent non-aqueous electrolyte having both the high load characteristics It becomes a battery.

The nonaqueous electrolyte battery 1 is manufactured, for example, as follows.

First, the positive electrode active material according to the present invention as described above is manufactured.

[0045] The surface of LiMnO ₂ particles or LiMn _1-y M y O ₂ particles to reform the LiMn ₂ O ₄ is, LiMnO ₂
The particle or the surface of LiMn _1-y M _y O ₂ particles by the action of aqueous solution of manganese ions, can be carried out by heat treatment. Manganese salts that form manganese ions include, for example, manganese nitrate, manganese acetate,
Manganese halides and the like can be mentioned, but it is desirable to use salts containing no nitrogen, phosphorus and halogen which do not generate harmful gas by heat treatment.

The concentration of the manganese ion aqueous solution is such that the manganese ion concentration D _Mn is 0 <D _Mn ≦ 0.58 (mol
/ L). D _Mn is 0.58
mol / l, LiMnO ₂ particles or LiM
The proportion of LiMn ₂ O ₄ formed on the surface of the n _{1 -y My} O ₂ particles is 20 wt% or more compared to the LiMnO ₂ particles or the LiMn _{1 -y My} O ₂ particles, and as a result, the capacity is increased. Will decrease. LiMnO ₂ or LiMn _1-y M y O ₂ and Li
When the weight ratio with Mn ₂ O ₄ (Mb / Ma) is 0.20,
Since the capacity is almost equal to that of a standard lithium ion positive electrode using LiCoO ₂ , there is no advantage in terms of capacity.

Therefore, LiMnO ₂ or LiMn _1-y M _y
When the weight ratio (Mb / Ma) between O ₂ and LiMn ₂ O ₄ is 0 <M
In order to satisfy the condition of b / Ma <0.20, the manganese ion concentration D _Mn of the manganese ion aqueous solution used for the surface modification should be in the range of 0 <D _Mn ≦ 0.58 (mol / l). Becomes indispensable.

It is preferable to add polyvinyl alcohol (PVA) to the aqueous manganese ion solution. By adding polyvinyl alcohol to the manganese ion aqueous solution, the appropriate viscosity is maintained in the manganese ion aqueous solution, and the manganese ion aqueous solution is more easily adsorbed on the surface of LiMnO ₂ particles or LiMn _{1- y My} O ₂ particles. The surface can be uniformly modified.

Then, using the obtained positive electrode active material, a coin-type nonaqueous electrolyte battery is manufactured as follows.

As the positive electrode 4, first, the positive electrode active material and the binder obtained as described above are dispersed in a solvent to prepare a slurry positive electrode mixture. Next, the obtained positive electrode mixture is uniformly applied on a positive electrode current collector and dried to form a positive electrode active material layer, whereby the positive electrode 4 is manufactured. Known binders can be used as the binder of the positive electrode mixture, and known additives and the like can be added to the positive electrode mixture.

For the negative electrode 2, first, a negative electrode mixture is prepared by dispersing a negative electrode active material and a binder in a solvent. Next, the obtained negative electrode mixture is uniformly applied on a negative electrode current collector and dried to form a negative electrode active material layer, thereby forming a negative electrode 2.
Is produced. As the binder of the negative electrode mixture, a known binder can be used, and a known additive or the like can be added to the negative electrode mixture. Further, metallic lithium serving as a negative electrode active material can be used as the negative electrode 2 as it is.

The non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent.

Then, the negative electrode 2 is accommodated in the negative electrode can 3, the positive electrode 4 is accommodated in the positive electrode can 5, and a separator 6 made of a polypropylene porous film or the like is disposed between the negative electrode 2 and the positive electrode 4. The non-aqueous electrolyte is injected into the negative electrode can 3 and the positive electrode can 5, and the negative electrode can 3 and the positive electrode can 5 are caulked and fixed via the insulating gasket 7, thereby completing the non-aqueous electrolyte battery 1.

In the above embodiment, a non-aqueous electrolyte battery using a non-aqueous electrolyte has been described as an example. However, the present invention is not limited to this. The present invention is also applicable to a solid electrolyte battery using a polymer solid electrolyte containing a simple substance or a mixture thereof, and a gel electrolyte battery using a gel solid electrolyte containing a swelling solvent.

Specific examples of the conductive polymer compound contained in the polymer solid electrolyte and the gel electrolyte include silicon, acryl, acrylonitrile, polyphosphazene-modified polymer, polyethylene oxide, polypropylene oxide, fluorine-based polymer, and the like. Examples thereof include a composite polymer, a crosslinked polymer, and a modified polymer of these compounds. Examples of the fluorine-based polymer include poly (vinylidene fluoride), poly (vinylidene fluoride-co-hexafluoropropylene), poly (vinylidene fluoride-co-tetrafluoroethylene), and poly (vinylidene fluoride-co-trifluoro). Ethylene) and the like.

Further, in the above-described embodiment, a description has been given of a secondary battery as an example. However, the present invention is not limited to this, and can be applied to a primary battery. In addition, the battery of the present invention has a cylindrical shape, a square shape, a coin shape, a button shape, and the like, and its shape is not particularly limited,
In addition, various sizes such as a thin type and a large size can be used.

[0057]

EXAMPLES Next, the present invention was performed to confirm the effects of the present invention.
Examples and comparative examples will be described. In the following embodiments, specific numerical values are described, but it goes without saying that the present invention is not limited to these.

Example 1 First, a positive electrode active material according to the present invention was synthesized as follows.

First, JNReimers et al., J. Electroche
m. Soc. V140, No. 12, p3396 (1993), a low-temperature LiMnO ₂ serving as a base material of a positive electrode active material.
Was synthesized.

Next, the surface of the LiMnO ₂ particles was modified and LiMn ₂ O ₄ was adhered to the surface of the LiMnO ₂ particles.

First, 0.1% of Mn (CH ₃ COO) ₂ was added to water.
The solution was dissolved at a concentration of mol / l to prepare a treatment solution. Next, 100 g of LiMnO ₂ particles and 10 m
1 was mixed to obtain a wet powder.

Next, the wet powder was air-dried for one hour.
Thereafter, the surface of the LiMnO ₂ particles is modified by heat-treating the powder at 100 ° C. for 1 hour to form LiMn ₂ O ₄
Thus, a positive electrode active material according to the present invention was obtained.

Next, a coin-type nonaqueous electrolyte battery was manufactured using the positive electrode active material obtained as described above.

80% by weight of the obtained positive electrode active material in dry weight, and 15% by weight of graphite (average particle size of 5 μm to 20 μm: trade name KS-15 Lonza) as a conductive agent;
Polyvinylidene fluoride (Aldrich # 1)
300) was mixed with dimethyl fluoride to obtain a positive electrode paste.

Next, this positive electrode paste was applied on an aluminum mesh as a positive electrode current collector, pelletized together with the aluminum mesh, and dried at 100 ° C. for 1 hour in a dry argon stream to obtain a positive electrode. . The positive electrode carries 60 mg of a positive electrode active material per one piece.

Further, a negative electrode was obtained by punching lithium metal into substantially the same diameter as the positive electrode.

Further, 1 mol of LiPF ₆ was added to an equal volume mixed solvent of propylene carbonate and dimethyl carbonate.
A non-aqueous electrolyte was prepared by dissolving at a concentration of 1 / l.

The negative electrode obtained as described above was accommodated in a negative electrode can, the positive electrode was accommodated in a positive electrode can, and a separator made of a porous film made of polypropylene or the like was disposed between the negative electrode and the positive electrode. A nonaqueous electrolyte solution was injected into the negative electrode can and the positive electrode can, and the negative electrode can and the positive electrode can were caulked and fixed via an insulating gasket, thereby completing a 2025 coin-type nonaqueous electrolyte battery.

Example 2 A cathode active material was synthesized in the same manner as in Example 1 except that polyvinyl alcohol was added at a rate of 0.1 mol / l to the processing solution when preparing the processing solution. A coin-type non-aqueous electrolyte battery was manufactured using the positive electrode active material.

[0070] without surface modification treatment for <Comparative Example> LiMnO ₂ particles, by using the LiMnO ₂ particles as a positive electrode active material, it was used to fabricate a non-aqueous electrolyte battery of coin type in the same manner as in Example 1.

The positive electrode active material obtained as described above was subjected to infrared absorption spectrum measurement and X-ray diffraction measurement to verify the surface modification.

The infrared absorption spectrum of the positive electrode active material of Example 2 which had been subjected to the surface modification treatment was compared with that of LiM used in Comparative Example 1.
FIG. 4 shows the infrared absorption spectra of nO ₂ and LiMn ₂ O ₄ together.

Further, the positive electrode active material of Example 2 subjected to the surface modification treatment, the LiMnO ₂ used in Comparative Example 1,
X-ray diffraction spectra of n ₂ O ₄ are shown in FIGS. 5 to 7, respectively.

Here, the infrared absorption spectrum measurement profile has a characteristic characteristic of LiMn ₂ O ₄ ,
If no LiMn ₂ O ₄ is observed in the X-ray diffraction spectrum, it can be considered that the surface of the material has been modified to LiMn ₂ O ₄ .

FIG. 4 shows that the positive electrode active material of Example 2 was obtained.
In the infrared absorption spectrum measurement profile of
_TwoO_FourWith a characteristic profile
5 to 7, X-rays of the positive electrode active material of Example 2 were obtained.
In the diffraction spectrum, LiMn _TwoO_FourIs not confirmed,
The surface of the positive electrode active material of Example 2 was LiMn._TwoO_FourChanged to
Can be considered as being quality.

The load characteristics of the manufactured non-aqueous electrolyte battery were measured. Initial charging was performed at a current density of 500 uA / cell until the open circuit voltage (OCV) reached 4.2 V and 0.05 V, and discharging was performed until the closed circuit voltage (CCV) reached 3.0 V. The current density at the time of discharge was 1C, 0.5C, 0.2C, 0.1C.
Was changed.

FIG. 8 shows the load characteristics of the nonaqueous electrolyte batteries of Examples 1, 2 and Comparative Examples. In FIG. 8, the results of Example 1 are indicated by ●, and the results of Example 2 are indicated by ×.
, And the result of the comparative example is indicated by ○.

As is apparent from FIG. 8, in the nonaqueous electrolyte batteries of Examples 1 and 2 using the positive electrode active material in which the surface of LiMnO ₂ particles was modified to LiMn ₂ O ₄ , the surface modification was performed. It can be seen that much better load characteristics were obtained compared to the non-aqueous electrolyte battery of the comparative example using LiMnO ₂ particles as the positive electrode active material.

Further, it can be seen that Example 2 in which polyvinyl alcohol was added to the surface-modified treatment solution gave better results than Example 1 in which polyvinyl alcohol was not added. This is thought to be because the addition of polyvinyl alcohol imparts an appropriate viscosity to the treatment solution, makes the treatment solution more easily adsorbed on the surface of the LiMnO ₂ particles, and can uniformly modify the surface. Can be

[0080]

According to the present invention, a high capacity LiMnO
₂ particles or LiMn _1-y M _y O to ₂ LiMn ₂ O ₄ in which the surface of the particles and excellent load characteristics by using a positive electrode active material comprising reformed, combines both the high capacity and high load characteristics An excellent nonaqueous electrolyte battery can be realized.

[0081]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a nonaqueous electrolyte battery according to the present invention.

FIG. 2 is a diagram showing load characteristics of low-temperature LiMnO ₂ .

FIG. 3 is a diagram showing load characteristics of LiMn ₂ O ₄ .

FIG. 4 is a positive electrode active material of Example 2 which has been subjected to a surface modification treatment.
And LiMnO used in Comparative Example 1. _TwoAnd LiMn_TwoO_FourWhen
FIG. 3 is a diagram showing an infrared absorption spectrum of the present invention.

FIG. 5 is a view showing an X-ray diffraction spectrum of a positive electrode active material of Example 2 which has been subjected to a surface modification treatment.

FIG. 6 is a view showing an X-ray diffraction spectrum of LiMnO ₂ used in Comparative Example 1.

FIG. 7 is a diagram showing an X-ray diffraction spectrum of LiMn ₂ O ₄ .

FIG. 8 is a diagram showing load characteristics of the nonaqueous electrolyte batteries of Example 1, Example 2, and Comparative Example.

[Explanation of symbols]

1 non-aqueous electrolyte battery, 2 negative electrode, 3 negative electrode can, 4
Positive electrode, 5 Positive electrode can, 6 Separator, 7 Insulating gasket

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01M 10/40 Z F-term (Reference) 4G048 AA04 AB04 AB05 AC06 AE05 5H029 AJ03 AK03 AL06 AL12 AM03 AM04 AM05 AM07 BJ03 CJ02 CJ08 CJ28 DJ12 DJ16 EJ12 HJ01 HJ02 HJ10 5H050 AA02 AA08 BA17 CA09 CB07 CB12 EA10 EA24 FA12 FA17 FA18 GA02 GA10 GA27 HA01 HA02 HA10

Claims (12)

[Claims] 1. A compound of the general formula LiMnO ₂ or LiMn _{1- y My}
A cathode active material, wherein LiMn ₂ O ₄ is present on the surfaces of compound particles represented by O ₂ (M is an element containing at least one of Al, B, Co and Ni). . 2. The positive electrode active material according to claim 1, wherein the surface of the compound particles is modified so that LiMn ₂ O ₄ is present on the surface of the compound particles. 3. The ratio of the weight Ma of the compound particles to the weight Mb of LiMn ₂ O ₄ present on the surface of the compound particles is in a range of 0 <Mb / Ma <0.20. The positive electrode active material according to claim 1, 4. A positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, wherein the positive electrode active material has a general formula LiMnO ₂ Or LiMn _1-y
(Of M is Al, B, Co or Ni, is an element comprising at least one.) M _y O ₂ non, characterized in that LiMn ₂ O ₄ is present on the surface of the compound particles represented by Water electrolyte battery. 5. The non-aqueous electrolyte battery according to claim 4, wherein the surface of the compound particles is modified so that LiMn ₂ O ₄ is present on the surface of the compound particles. 6. The ratio of the weight Ma of the compound particles to the weight Mb of LiMn ₂ O ₄ present on the surface of the compound particles is in a range of 0 <Mb / Ma <0.20. The non-aqueous electrolyte battery according to claim 4, wherein 7. A manganese ion solution is treated with a general formula LiMnO ₂ or LiMn _{1- y My} O ₂ (M is Al, B,
It is an element containing at least one of Co and Ni. A method for producing a positive electrode active material, comprising adding to the compound particles represented by the formula (1) and then heating to obtain a positive electrode active material having LiMn ₂ O ₄ present on the surface of the compound particles. 8. The production of a positive electrode active material according to claim 7, wherein the manganese ion concentration D _Mn in the manganese ion solution is in the range of 0 <D _Mn ≦ 0.58 (mol / l). Method. 9. The method for producing a positive electrode active material according to claim 7, wherein polyvinyl alcohol is added to said manganese ion solution. 10. A method for manufacturing a nonaqueous electrolyte battery comprising: a positive electrode having a positive electrode active material; a negative electrode having a negative electrode active material; and a nonaqueous electrolyte interposed between the positive electrode and the negative electrode. , in the synthesis of the positive electrode active material, a manganese ion solution, a base formula LiMnO ₂ or LiMn _1-y M y
After being added to compound particles represented by O ₂ (M is an element containing at least one of Al, B, Co and Ni), the surface of the compound particles is heated by heating to give LiM.
A method for producing a non-aqueous electrolyte battery, comprising obtaining a positive electrode active material in which n ₂ O ₄ is present. 11. The non-aqueous electrolyte battery according to claim 10, wherein the manganese ion concentration D _Mn in the manganese ion solution is in the range of 0 <D _Mn ≦ 0.58 (mol / l). Production method. 12. The method according to claim 10, wherein polyvinyl alcohol is added to said manganese ion solution.
A method for producing the nonaqueous electrolyte battery according to the above.