JP2001266874A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high voltage and high energy lithium ion secondary battery having a lithium manganese oxide of a spinel structure as a positive electrode that is excellent in charge and discharge capacity and charge and discharge cycle characteristics. SOLUTION: This is a lithium ion secondary battery which comprises a positive electrode that has a positive electrode active material comprising lithium manganese oxide of a spinel structure as expressed in the chemical formula LixMnOy (wherein x is a real number 0.55<=x<=0.65, y is a real number 1.80<=y<=2.20), a negative electrode and a non-aqueous electrolyte containing lithium ion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium ion secondary battery having a high discharge capacity and excellent charge / discharge cycle characteristics.

[0002]

2. Description of the Related Art In recent years, with advances in electronic technology, miniaturization of electronic devices such as personal computers and mobile phones has been rapidly advancing. Accordingly, these power supplies also need to be reduced in size, and lithium-ion batteries have been actively developed recently. On the other hand, electric vehicles are attracting attention due to environmental problems, and some of them are being put to practical use. In order to further generalize this electric vehicle, a battery having a large capacity and excellent cycle characteristics is indispensable as a power source, and the use of a lithium ion battery is being studied for such a large battery.

As a positive electrode active material for a lithium ion battery,
Manganese dioxide is used for primary batteries, and vanadium oxide and lithium cobalt compounds are used for secondary batteries. In addition, lithium manganese oxides such as lithium manganate are being actively developed because the manganese compound as a raw material is less expensive and less toxic than the above-mentioned cobalt compound.

[0004] Among these lithium manganates, lithium manganate having a spinel structure has a three-dimensional structure. Therefore, when the lithium manganate is used as a positive electrode active material of a lithium ion secondary battery and charged and discharged, it has a crystal structure. It is possible to stably dope and undope lithium ions into the crystal lattice without destruction. In particular, the deterioration of deintercalation is small, and the discharge voltage is high and stable. It is very promising as a positive electrode active material for batteries, and has been actively studied in recent years for practical use.

For example, JP-A-1-109662 discloses that lithium manganate represented by LiMn ₂ O ₄ having a spinel structure (Li / Mn atomic ratio: 0.5) is used as a positive electrode active material, and a lithium alloy is used as a negative electrode active material. A non-aqueous secondary battery using a non-aqueous electrolyte containing lithium ions is disclosed. Also, in Japanese Patent Application Laid-Open No. 10-50316,
An organic electrolyte secondary battery including, as an anode active material, a cathode containing lithium and LiMn ₂ O ₄ synthesized from lithium carbonate and manganese dioxide is disclosed.

The prior art of the lithium ion secondary battery using lithium manganate as a positive electrode active material is more effective than a battery using a manganese dioxide or a chalcogenide of titanium, molybdenum or niobium as a positive electrode active material. The charge / discharge capacity and cycle characteristics have been improved.

However, in recent years, with the demand for higher voltage and higher energy of the secondary battery, such a secondary battery has a larger charge / discharge capacity and excellent charge / discharge cycle characteristics. However, these prior arts have not yet satisfied these requirements, and further improvements have been desired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium manganese oxide having a spinel structure excellent in charge / discharge capacity and charge / discharge cycle characteristics for a high voltage and high energy lithium ion secondary battery. To provide a lithium ion secondary battery using as a positive electrode active material.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that a positive electrode, a negative electrode, and a lithium manganate having a spinel structure and a specific composition are used as a positive electrode active material. The inventors have found that a lithium ion secondary battery comprising a nonaqueous electrolyte containing lithium ions has a high charge / discharge capacity and excellent charge / discharge cycle characteristics, and has completed the present invention.

That is, in the lithium ion secondary battery of the present invention, the positive electrode active material has the chemical formula Li _x M having a spinel structure.
nO _y (where x is a real number of 0.55 ≦ x ≦ 0.65, y
Indicates a real number satisfying 1.80 ≦ y ≦ 2.20. ), A positive electrode made of lithium manganate, a negative electrode, and a non-aqueous electrolyte containing lithium ions.

[0011]

Lithium manganate having the above spinel structure DETAILED DESCRIPTION OF THE INVENTION, represented by the chemical formula Li _x MnO _y.
In the formula, x is 0.55 ≦ x ≦ 0.65, preferably 0.5
Real number of 7 ≦ x ≦ 0.60, particularly preferably x = 0.58
Alternatively, 0.59, y is a real number satisfying 1.80 ≦ y ≦ 2.20, preferably 1.90 ≦ y ≦ 2.10, particularly preferably y = 2.00. Specifically, Li _0.58 Mn
Those having a composition of O _2.00 or Li _0.59 MnO _2.00 are preferably used. x and y are out of the above range,
That is, the Li / Mn atomic ratio is less than 0.55,
If it exceeds 0.65, excellent charge / discharge capacity and charge / discharge cycle characteristics cannot be obtained for a lithium ion secondary battery of high voltage and high energy.

The lithium manganate used in the present invention may be a simple compound, a manganese composite oxide containing lithium manganate having a spinel structure and a manganese oxide such as manganese oxide, or lithium manganate. A mixture of manganese oxides may be used. In the case of the manganese composite oxide or the mixture, the other component of lithium manganate having a spinel structure is mainly manganese (III) oxide, and in some cases, may include lithium manganate having a perovskite structure. Its composition is usually 5% lithium manganate having a spinel structure.
0 to 100% by weight, preferably 80 to 100% by weight, manganese (III) oxide is 0 to 50% by weight, preferably 0 to 50% by weight.
-20% by weight.

The method for producing the lithium manganate having the spinel structure is not particularly limited, and a known method can be employed. Specifically, it is produced by using a lithium compound and a manganese compound as main raw materials by a solid phase reaction, a solid phase sintering method, a melt impregnation method, a hydrothermal method, a liquid phase reaction method, an electrodeposition method or a chelate method. Here, examples of the lithium compound include lithium hydroxide, lithium chloride, lithium nitrate, lithium oxide, lithium carbonate, lithium acetate, and the like. Examples of the manganese compound include manganese oxide, manganese carbonate, manganese halide such as manganese chloride, and γ. —MnOOH and the like.

Among the above production methods, a method of directly contacting and reacting a manganese halide and a lithium compound in a liquid phase at 100 ° C. or lower to obtain lithium manganate having a spinel structure (hereinafter referred to as “direct liquid phase reaction method”) Is preferred, and when used as a positive electrode material of a lithium ion secondary battery, lithium manganate exhibiting excellent battery characteristics can be obtained. Manganese halides used in this direct liquid phase reaction method are specifically manganese (II) dichloride and manganese (III) trichloride, including anhydrides and hydrated crystals. Of these, manganese (II) dichloride
Is stable and preferred. The purity is preferably higher to obtain higher purity lithium manganate. Specifically, the purity is 99% by weight or more, preferably 99.9% by weight or more.
It is preferable that other metal components such as i and Na are each 0.1% by weight or less.

When a halide is used as a manganese compound in the solid-phase method or the solid-phase sintering method, a halogen component remains in lithium manganate and is difficult to remove.
The use of manganese halide as a raw material has heretofore been avoided since it has an undesirable effect on its characteristics when used as a battery material. However, in the above-mentioned direct liquid phase reaction method, by using manganese halide as an aqueous solution and reacting with a lithium compound in a liquid phase, only lithium manganate is produced as a solid, and unnecessary halides are not mixed. It is possible to produce lithium manganate. Manganese halides such as manganese chloride are cheaper than conventionally used manganese compounds, and it has become possible to produce lithium manganate at lower cost. For this reason, manganese chloride is preferred as the manganese halide.

Next, lithium compounds used for producing lithium manganate by a direct liquid phase reaction method include:
Specifically, lithium hydroxide, lithium chloride, lithium iodide, lithium bromide, lithium nitrate, lithium nitrite, lithium sulfate, lithium hydrogen sulfate, lithium carbonate,
Compounds capable of forming an aqueous solution such as a lithium salt such as lithium hydrogen carbonate, lithium acetate, lithium oxide, lithium peroxide, and lithium chlorate are exemplified. These lithium compounds can be used alone or in combination of two or more.
Of these, lithium hydroxide, lithium chloride and lithium nitrate are particularly preferably used.

Further, it is desirable to use lithium hydroxide and lithium chloride in combination as a raw material as a lithium source. The manganese halide and the lithium compound are brought into contact with each other in a liquid phase to cause a reaction, and it is desirable that the pH is adjusted in an alkaline region. Lithium hydroxide acts not only as a raw material as a lithium source but also as an alkali source. It is preferably used. Further, as another alkali source of lithium hydroxide, a hydroxide such as sodium hydroxide or potassium hydroxide can be used.

As for the lithium compound, as in the case of the manganese halide, a higher lithium compound is preferable in order to obtain higher purity lithium manganate.
It is preferable that the purity is 99% by weight or more, preferably 99.9% by weight or more, and in particular, each of other metal components such as Fe, Ni, and Na as impurities is 0.1% by weight or less.

In addition to the above-mentioned manganese halide and lithium compound, it is desirable to use an oxidizing agent in the direct liquid phase reaction method to oxidize manganese to a desired valence. In particular, when manganese chloride and a lithium compound are brought into contact with each other in a liquid phase to cause a reaction, it is preferable to allow an oxidizing agent to coexist. Specific examples of the oxidizing agent include oxidizing agents such as hydrogen peroxide, potassium permanganate, and chloric acid. Among them, particularly, hydrogen peroxide is preferably used without any impurity element mixed into the product after the reaction. Can be

The method for producing lithium manganate by the direct liquid-phase reaction method described above is characterized in that the above components are used as raw materials for contact and reaction in a liquid phase at 100 ° C. or lower. The term “react” means that the above-mentioned manganese halide and lithium compound are brought into contact with each other in the state of an aqueous solution to cause a reaction, and the contact reaction is not carried out in a state where these raw materials are suspended in a liquid phase. This is a method for producing lithium manganate having a spinel structure by a so-called gel-sol method or a direct synthesis method. Also, this direct liquid phase reaction method prepares aqueous solutions of these compounds,
The reaction is performed in a liquid phase, and may contain a water-soluble organic solvent such as alcohol.

The reaction temperature is 100 ° C. or lower, but preferably 80 to 100 ° C., more preferably 85 to 95 ° C. At this time, the aqueous solution of the manganese halide and the lithium compound may be brought into contact at room temperature and then reacted by raising the temperature. However, in the case of continuous production, it is preferable that the reaction be carried out by heating to the reaction temperature in advance. The reaction time is usually 1 minute or more, preferably 1 minute to 15 hours, after the respective raw materials are brought into contact and a predetermined reaction temperature is reached.

In the direct liquid phase reaction method, the contact method and the reaction method are not particularly limited, but the following methods can be employed. 1) A mixed aqueous solution of a lithium compound and a manganese halide is prepared at room temperature, and then heated to react. 2) A normal temperature manganese halide aqueous solution is dropped into a normal temperature lithium compound aqueous solution and brought into contact, and then the temperature is raised to cause a reaction. 3) A normal temperature manganese halide aqueous solution is dropped into the preheated lithium compound aqueous solution and brought into contact, and then the temperature is raised to cause a reaction. 4) A preheated manganese halide aqueous solution is dropped into a preheated lithium compound aqueous solution, brought into contact with the solution, and then reacted. 5) A normal temperature lithium compound aqueous solution is dropped into a normal temperature manganese halide aqueous solution and brought into contact with the solution, and then the temperature is raised to cause a reaction. 6) A mixed aqueous solution of manganese halide and lithium compound at normal temperature is dropped and brought into contact with an aqueous solution of lithium compound at normal temperature, and then the temperature is raised to cause a reaction. 7) A mixed aqueous solution of manganese halide and lithium compound at room temperature is dropped and brought into contact with the preheated aqueous solution of lithium compound, and then the temperature is raised to cause a reaction. 8) A mixed aqueous solution of a manganese halide and a lithium compound, which has been preheated, is dropped into an aqueous solution of a lithium compound which has been preheated, brought into contact, and then heated to react.

An oxidizing agent such as hydrogen peroxide is added at any stage of the above-mentioned contact and reaction. For example, the oxidizing agent may be added to an aqueous solution of manganese halide before contacting with a lithium compound or may be added before contacting with a lithium compound. It is added to an aqueous solution of the compound or after the contact between the manganese halide and the lithium compound. Among these, it is preferable to add the manganese halide to the aqueous solution of manganese halide before contacting with a lithium compound, which is a preferable method since the valence of manganese can be adjusted in advance.

The amount ratio of each of the above raw materials is arbitrary as long as lithium manganate having a desired composition ratio can be obtained. Preferably, the amount of the lithium compound is 0.3 to 0.7 mol, more preferably 0.4 to 0.7 mol per mol of manganese halide. 0.6 mole,
The oxidizing agent such as hydrogen peroxide is used in an amount of 0.3 to 2 mol, more preferably 0.6 to 1.5 mol. When lithium hydroxide and lithium chloride are used in combination as a lithium compound, lithium hydroxide is used in an amount of 1 mol per mol of manganese halide.
~ 5 mol, preferably 3-3.5 mol, lithium chloride is 0.
It is 3 to 0.7 mol, preferably 0.4 to 0.6 mol.

Further, each of the above-mentioned raw materials is brought into contact with an aqueous solution, and the concentration of each aqueous solution at that time is not particularly limited. Preferably, the aqueous solution of manganese halide is 0.1 to 2 mol / l,
It is more preferably 0.8 to 1.2 mol / l, and the aqueous lithium compound solution is 0.05 to 1 mol / l, more preferably 0.4 to 0.6 mol / l. When lithium hydroxide and lithium chloride are used in combination as the lithium compound, the aqueous solution of lithium hydroxide is 1 to 5 mol / l, preferably 3 to 3.5 mol / l, and lithium chloride is 1 mol of manganese halide.
It is from 0.3 to 0.7 mol / l, preferably from 0.4 to 0.6 mol / l.

Further, the pH of the liquid phase at the time of contacting and reacting in the liquid phase as described above is usually 7-14, preferably 7-11, and when lithium hydroxide is used as the lithium compound, Adjust according to the aqueous solution concentration.

As described above, each raw material is contacted and reacted in a liquid phase to obtain lithium manganate having a spinel structure.
The obtained lithium manganate is separated from the liquid phase if necessary and dried. When the obtained lithium manganate is separated from the liquid phase, it is desirable to wash the obtained lithium manganate with pure water or alcohol to remove halogen and other free unreacted components remaining in the liquid phase. . As the separation means, a commonly used method such as decantation, filtration, or centrifugation can be adopted. The drying is performed while heating by vacuum drying or the like.

As described above, lithium manganate having a direct spinel structure is produced by a direct liquid phase reaction method in which a manganese halide and a lithium compound are reacted in a liquid phase, but the crystallinity of lithium manganate is further improved. For this purpose, the lithium manganate obtained by the above method can be heat-treated. The temperature at this time is usually 400 to 1000 ° C, preferably 400 to 80 ° C.
0 ° C., more preferably 500 to 750 ° C., and the heat treatment time is usually 1 to 30 hours, preferably 2 to 10 hours,
More preferably, it is 4 to 8 hours. The atmosphere for the heat treatment is usually in the air, but the heat treatment may be performed in an inert atmosphere such as argon or nitrogen or an oxygen atmosphere.

The lithium manganate obtained as described above is a single oxide of lithium manganate having a spinel structure or a composite oxide or a mixture with manganese oxide, and has an average particle diameter of 1 to 50 μm and a specific surface area of 10 μm. -10
0 m ² / g, and the BET diameter is 0.01 to 0.2 μm.

As described above, in the direct liquid phase reaction method, since the reaction is performed at a lower temperature and the reaction is carried out in a homogeneous solution as compared with the solid phase method or the solid phase sintering method, the particle size is small and the specific surface area is large. Lithium manganate having a uniform spinel structure can be obtained. Therefore, it is possible to obtain an electrode material which is suitable for an electrode material and in which deterioration of charge / discharge cycle characteristics is particularly small. Further, as in the synthesis by the hydrothermal method, 100 ° C. to 30 ° C.
Since a reaction at a high temperature of 0 ° C. and a high pressure of 300 atm is not required, energy cost and equipment cost can be suppressed, and production at low cost is possible. Furthermore, since the pulverization of the manganese raw material is not required unlike the melt impregnation method, there is no possibility that impurities such as iron are mixed during the pulverization, so that it is advantageous in obtaining a high-purity product.

In the lithium ion secondary battery of the present invention,
Examples of the active material of the negative electrode constituting this secondary battery include:
For example, metal lithium, lithium alloy, polyacetylene,
Conductivity by doping lithium ions into lipirole, etc.
Polymer, TiS_Two, MoS _Two, NbSe_ThreeEtc. metal
Compounds obtained by doping lithium ions into chalcogenides
Things, WO_Two, MoO_Two, Fe_TwoO_Three, TiS_TwoEtc. inorganic
Compounds, graphite, etc.
However, a substance containing lithium is preferable, and particularly preferable is lithium.
It is a titanium alloy. Specifically, lithium and aluminum
, Zinc, tin, lead, bismuth, cadmium, silver, ter
Alloys with at least one or more metals such as
But an alloy of lithium and aluminum, or lithium
An alloy of silver, silver and tellurium is preferably used.

When a lithium alloy is used as the negative electrode active material, the lithium content in the alloy depends on the other metals to be combined, but is 10 to 95% by atomic ratio, preferably 4 to 95%.
0 to 70%. The lithium alloy can be obtained by a known method, and examples thereof include a method of melting and alloying, an electrolytic deposition method in an electrolytic solution, a pressure bonding method in an electrolytic solution, and a hot-dip plating method. Among these methods, the electrolytic deposition method is preferable. Specifically, after an aluminum plate is subjected to surface treatment (etching) with an acid such as hydrofluoric acid or hydrochloric acid, lithium is used as a counter electrode, a voltage is applied in an electrolytic solution, and lithium is precipitated on the surface of the aluminum plate. Obtain a lithium alloy. The aluminum and lithium used at this time are desirably high in purity with little other metal elements, specifically 3N (99.9%) or more, preferably 4N or more.
N (99.99%) or more. When a lithium alloy is prepared by these methods, a diffusion barrier layer such as nickel, cobalt, iron or the like or silver,
Form a wetting promoting material layer of copper, zinc, magnesium, etc.

The non-aqueous electrolyte containing lithium ions that constitutes the lithium ion secondary battery of the present invention is composed of a solvent and a lithium salt. As the solvent, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ -Organic solvents such as butyrolactone, methyl formate, methyl acetate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, ethyl monoglyme Can be mentioned. As the lithium salt, LiPF ₆ , LiClO ₄ , LiCF ₃ SO
₃ , LiN (CF ₃ SO ₂ ) ₂ , LiBF _{4 and the} like. The lithium salt is dissolved in the solvent to form a non-aqueous electrolyte, and the positive electrode and the negative electrode are combined to form a lithium ion secondary battery of the present invention.

As described above, the feature of the lithium ion secondary battery of the present invention is that the positive electrode active material has a spinel structure and uses a positive electrode made of lithium manganate represented by the chemical formula Li _0.55-0.65 MnO _1.80-2.20. For example, LiMn ₂ O ₄ (Li _0.5 Mn) having a conventional spinel structure
Compared to O ₂ ), there are more Li atoms than Mn atoms. Therefore, the crystal structure is more stable, and the amount of Mn eluted in the electrolytic solution during charge and discharge is small, so that the charge and discharge capacity is excellent and the charge and discharge cycle characteristics are excellent.

[0035]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Further, X-ray diffraction measurement (Table 1), average particle diameter measurement, and specific surface area measurement of lithium manganate used in Examples and Comparative Examples were performed by the following methods. (X-ray diffraction measurement)

[0036]

[Table 1] ──────────────────────────────────── Diffractometer RAD-1C (Rigaku Corporation) X-ray tube Cu tube voltage / tube current 40 kV, 30 mA slit DS-SS: 1 degree, RS: 0.15 mm Monochromator Graphite Measurement interval 0.002 degree Counting method Constant clock method 法────────────────────────────

(Measurement of Average Particle Size) The average particle size was measured using a laser diffraction type particle size analyzer (LA-700 manufactured by Horiba, Ltd.).

(Measurement of Specific Surface Area) The specific surface area was measured by the BET method.

Example 1 (Preparation of lithium manganate) 3.2 l in a 2 l flask equipped with a 1 l dropping funnel and a stirrer.
0.8 liter of a 5 mol / liter lithium hydroxide aqueous solution was charged and heated to 90 ° C. On the other hand, 0.4 liter of a 1.0 mol / l manganese dichloride aqueous solution, 0.4 liter of a 0.5 mol / l lithium chloride aqueous solution, and 0.24 mol of hydrogen peroxide were charged into the dropping funnel, and the mixture was homogenized. A mixed solution was formed. Then, while stirring,
The mixed solution was dropped into a heated aqueous solution of lithium hydroxide over 60 minutes from a dropping funnel. 1 hour after dropping,
The reaction was performed at 90 ° C. and cooled to room temperature. Thereafter, the operation of centrifuging the suspension containing the obtained solid product and removing the supernatant was repeated three times for washing. The obtained solid was dried at 120 ° C. for 24 hours to obtain lithium manganate. When the obtained lithium manganate was analyzed by X-ray diffraction, a peak of lithium manganate having a spinel structure appeared. When the composition was analyzed, Li / M
The n atomic ratio was 0.58. Further, the average particle size is 20.
7 μm, specific surface area 13.1 m ² / g, BET diameter 0.3
It was 11 μm. Further, the spinel-structured lithium manganate obtained above was subjected to a heat treatment at 700 ° C. for 5.5 hours. When the composition of the obtained lithium manganate was analyzed, the Li / Mn atomic ratio was 0.58.

(Preparation of Lithium-Aluminum Alloy) An aluminum plate having a purity of 99.99% was etched in 5% hydrofluoric acid. Next, Li in propylene carbonate
It was prepared by depositing lithium on the aluminum plate at a current density of 1 mA / cm ² for 24 hours using a lithium foil as a counter electrode in a 30 ° C. electrolytic solution in which PF ₆ was dissolved at a concentration of 1 mol / dm ³ . .

(Evaluation of Characteristics of Lithium Ion Secondary Battery-I)
With respect to the lithium manganate and lithium-aluminum alloy prepared as described above, the lithium ion secondary battery characteristics were evaluated under the following conditions.

Preparation of Positive Electrode: A lithium manganate powder, acetylene black and polytetrafluoroethylene were kneaded at a weight ratio of 8: 1: 1 and pressed and molded.
It dried under reduced pressure at 00 degreeC for 12 hours, and was set as the positive electrode.

Preparation of Battery and Measurement of Discharge Capacity:
The above-mentioned lithium-aluminum
Alloy, lithium foil for the reference electrode, and polyether for the separator
The discharge capacity of the positive electrode was measured using a pore membrane made of titanium. Electric
For lysis, propylene carbonate, ethylene carbonate
Solvent and a mixture of 1,2-dimethoxyethane (by volume)
1: 1: 1) to LiPF₆1 mol / dm ^ThreeDissolved at a concentration of
Was used. The temperature was 30 ° C. Charging is 1mA / cm^TwoNo electricity
Run until the potential reaches 4.4 V with reference to the reference pole at the current density
The discharge is at the same current density and the potential is 3.5 V with respect to the reference electrode.
Until it reaches. Repeat this charge / discharge operation,
The discharge capacity was determined from the obtained charge / discharge curve. The result
It is shown in Table 2.

COMPARATIVE EXAMPLE 1 0.85 3.25 mol / l aqueous solution of lithium hydroxide
An experiment was conducted in the same manner as in Example 1 except that the liter was changed to 0.6 liter to prepare lithium manganate. When the composition of the obtained lithium manganate was analyzed, Li /
The Mn atomic ratio was 0.31. The discharge capacity of this lithium manganate was measured in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 2 Lithium manganate was prepared in the same manner as in Example 1, except that 0.60 mol of hydrogen peroxide was used instead of 0.24 mol of hydrogen peroxide. When the composition of the obtained lithium manganate was analyzed, the Li / Mn atomic ratio was 0.80. The discharge capacity of this lithium manganate was measured in the same manner as in Example 1, and the results are shown in Table 2.

[0046]

[Table 2]

Example 2 (Preparation of lithium manganate) Lithium manganate prepared in the same manner as in Example 1 was used. (Preparation of lithium-aluminum alloy) A lithium-aluminum alloy prepared in the same manner as in Example 1 was used.

(Evaluation of Lithium Ion Secondary Battery Characteristics-II)
With respect to the lithium manganate and lithium-aluminum alloy prepared as described above, the lithium ion secondary battery characteristics were evaluated under the following conditions. The production of the positive electrode was the same as in Example 1.

Preparation of Battery and Measurement of Charge / Discharge Capacity: A positive electrode was prepared in the same manner as in Example 1 using the above lithium manganate, and a battery using the above lithium-aluminum alloy as the negative electrode was prepared. Was done. The same separator and electrolyte used for the discharge capacity measurement in Example 1 were used. Charging was performed at a current density of 1 mA / cm ² until the voltage reached 4.1 V, and discharging was performed at the same current density until the voltage reached 3.0 V. This charge / discharge operation was repeated, and the discharge capacity of lithium manganate was determined from the obtained charge / discharge curve. Table 3 shows the results.

[0050]

[Table 3]

From Table 2, it can be seen that the lithium ion secondary battery of the present invention has a large discharge capacity. Further, it can be seen from Table 3 that the discharge capacity does not decrease even when the charge / discharge operation is repeatedly performed. It can be seen that the cycle characteristics are extremely excellent.

[0052]

As described above, according to the present invention, the chemical formula Li _x MnO _y (where x is 0.55 ≦ x ≦ 0.6)
5 is a real number, and y is a real number satisfying 1.80 ≦ y ≦ 2.20. ) Is used as a positive electrode active material, and a lithium ion secondary battery is composed of this, a negative electrode and a non-aqueous electrolyte containing lithium ions. A lithium ion secondary battery having excellent discharge cycle characteristics can be obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Sakai 3-3-5 Chigasaki, Chigasaki City, Kanagawa Prefecture Toho Titanium Co., Ltd. 6-12-19 Chuo, Yamato-shi, Kanagawa Pref. 3-305 River No. 3 Heights City Kazuharu Sobue 1-940 Kosugi Gotencho, Nakahara-ku, Kawasaki-shi, Kanagawa F-term (reference) 5H029 AJ05 AK03 AL12 AM03 AM04 AM05 AM07 CJ02 CJ14 CJ28 DJ17 HJ02 HJ14 5H050 AA07 BA17 CA09 CB12 DA02 DA03 FA17 FA19 GA02 GA15 GA27 HA02 HA14

Claims (9)

[Claims] 1. A chemical formula of Li _x MnO _{y in} which the positive electrode active material has a spinel structure, wherein x is 0.55 ≦ x ≦ 0.65.
Represents a real number satisfying 1.80 ≦ y ≦ 2.20. )
A lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte containing lithium ions represented by the following formula: 2. The lithium ion secondary battery according to claim 1, wherein the active material of the negative electrode is a lithium alloy. 3. The lithium ion secondary battery according to claim 1, wherein the active material of the negative electrode is an alloy of lithium and aluminum. 4. The lithium ion secondary battery according to claim 1, wherein the active material of the negative electrode is an alloy of lithium and aluminum obtained by an electrolytic deposition method. 5. The lithium ion secondary battery according to claim 1, wherein the lithium manganate is obtained by contacting and reacting a manganese halide and a lithium compound in a liquid phase at 100 ° C. or lower. battery. 6. The lithium ion secondary battery according to claim 5, wherein said manganese halide is manganese chloride. 7. The method according to claim 1, wherein the lithium compound is lithium hydroxide,
At least one selected from lithium chloride, lithium iodide, lithium bromide, lithium nitrate, lithium nitrite, lithium sulfate, lithium hydrogen sulfate, lithium carbonate, lithium hydrogen carbonate, lithium acetate, lithium oxide, lithium peroxide and lithium chlorate The lithium ion secondary battery according to claim 5, which is a seed. 8. Manganese chloride and lithium compound in 10
7. The lithium ion secondary battery according to claim 6, wherein, when contacting and reacting in a liquid phase at 0 ° C. or lower, an oxidizing agent is allowed to coexist to prepare lithium manganate. 9. The method according to claim 8, wherein the oxidizing agent is hydrogen peroxide.
4. The lithium ion secondary battery according to 1.