JP2000251894A - Nonaqueous secondary battery, and usage thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery of high capacity superior in a charge load characteristic, in which inexpensive manganese rich in terms of resource is used as a constitutional element for a positive active material. SOLUTION: In this nonaqueous secondary battery having a positive electrode using a positive active material doped/dedoped with an lithium ion by charge- discharge, a negative electrode and a separator, a spherical or elliptic spinel-type lithium manganese oxide, which is expressed by the general formula LixMnyO4-z, where 0.48<=y/4-z<=0.52 and 0<z<=0.15 are satisfied for y and z in the formula, and x is regulated within the range of 0.10<=x<=0.95 in both charge and discharge conditions, is used for the positive active material, and a release terminal voltage of the battery is set at 3 V or more. A spinel-type lithium manganese oxide of another element (other than manganese) solid solution type, in which one portion of the manganese element is substituted by another element such as aluminium and boron, may be also used for the spinel-type lithium manganese oxide hereinbefore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery, and more particularly, to a high-capacity non-aqueous secondary battery having excellent charge load characteristics and a high capacity.

[0002]

2. Description of the Related Art In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers and the practical use of electric vehicles, secondary batteries of small size, light weight and high capacity have been required. . At present, a lithium ion secondary battery using LiCoO ₂ as a positive electrode active material and a carbon-based material as a negative electrode active material has been commercialized as a high capacity secondary battery that meets this demand. In the charge / discharge reaction of this battery, lithium ions released from crystals of the positive electrode active material LiCoO ₂ during charging are inserted into the carbon-based material as the negative electrode active material, and lithium ions inserted into the carbon-based material during discharging are charged. It is based on a topochemical electrochemical reaction that desorbs and re-inserts into the LiCoO ₂ crystal. LiC used as a positive electrode active material of this battery
Since oO ₂ is easy to manufacture and easy to handle, it has been evaluated as a suitable positive electrode active material and has been widely used.

[0003] However, LiCoO ₂ is produced from a rare metal, cobalt (Co), as a raw material.
It is expected that resource shortages will become serious in the future. In addition, since the price of cobalt itself is high and the price fluctuates greatly, it is desired to develop a cathode material that is inexpensive and has a stable supply.

[0004] Therefore, research has been conducted on lithium ion secondary batteries using lithium manganese oxide, lithium nickelate, lithium titanate, etc. having a spinel structure as a positive electrode active material instead of LiCoO _2. The price of the constituent elements among the products is low,
Spinel-type lithium manganese oxide with stable supply of manganese is attracting attention as a positive electrode active material replacing LiCoO ₂

[0005] The lithium manganese oxide having the spinel structure is less expensive than other lithium composite oxides.
In addition, the lithium ion for a hybrid electric vehicle (HEV) or an electric vehicle (PEV), which is used for large batteries and requires a large amount of batteries, because of its high thermal stability in a charged state and low reactivity with an electrolytic solution. It is expected as a positive electrode material for secondary batteries.

[0006] The spinel-type lithium
Lithium oxide is Li_TwoMn_FourO ₉, Li_FourMn_FiveO
₁₂, LiMn_TwoO_FourAmong them, LiMn_TwoO
_FourCan charge and discharge in the 4V region with respect to lithium potential
Therefore, research has been actively conducted (Japanese Unexamined Patent Publication No.
No. 6824, Japanese Patent Application Laid-Open No. 7-73883, Japanese Patent Application Laid-Open
JP-A-7-230802, JP-A-7-245106
Information).

[0007]

The non-aqueous secondary battery has a very low ion conductivity in the battery, and therefore has a large internal resistance of the battery. Due to the large polarization, a charging method using both constant current charging (CC) and constant voltage charging (CV) is used for charging.

[0008] To explain this in detail, the voltage rises to a predetermined end-of-charge voltage by performing constant-current charging. At this time, both the positive electrode active material and the negative electrode active material have low diffusion rates of lithium ions. Polarization is very large and apparently reaches the end-of-charge voltage, but the actual voltage is lower than the predetermined end-of-charge voltage. Not available. Therefore, after performing the constant current charging, the constant voltage charging is performed so that both the positive electrode active material and the negative electrode active material can be sufficiently used. In this constant voltage charging, the charging current value becomes smaller as time passes to maintain a constant voltage, as compared with the constant current charging. With the decrease in the charging current value, the polarization of each electrode becomes smaller, and as the polarization becomes smaller, it becomes possible to allow more current to flow and charge up to a predetermined end voltage.

Therefore, when the load characteristics during charging are poor, the amount of electricity charged by constant voltage charging is larger than the amount of electricity charged by constant current charging. In such a case, in the case of constant voltage charging, as described above, the charging current value decreases with the lapse of time, so that there is a problem that it takes a long time to perform charging to a predetermined end voltage. Therefore, as a charging method, it is preferable to charge most of the electric capacity by constant current charging as much as possible in order to shorten the charging time. Therefore, as a positive electrode active material of a non-aqueous secondary battery,
It is required to have a large capacity for constant-current charging, a short charging time for constant-voltage charging, and a charge that can be completed in a short time as a whole.

For example, in a device such as a video camera, a mobile phone, an electric shaver, or a power tool using a secondary battery, the built-in secondary battery or the battery pack is often charged immediately before use, so that the time is as short as possible. It is required that charging be completed. In particular, in the case of a device using a lithium ion secondary battery as a power source, the discharge end voltage of a unit cell in a battery pack is almost always 3 V or more, and the time required for charging the battery capacity at a voltage of 3 V or more. Needs to be shortened.

When charging as described above, Li
Since the crystal of CoO ₂ has a layered structure, the doping / de-doping of lithium in the crystal proceeds relatively smoothly, whereas LiMn ₂ O ₄ does not have a layered crystal structure. The diffusion rate of doping / de-doping of ions is low, so the capacity for constant current charging is small,
At present, the charge load characteristics are inferior to LiCoO ₂ due to the large polarization. In particular, when used for a power source of a portable device or the like, it is necessary to charge the battery in a short period of time.
_{When 2} O ₄ is used as the positive electrode active material, when a large charging current flows, the polarization of the positive electrode and the negative electrode, particularly the polarization of the positive electrode, is further increased. Therefore, it is difficult to shorten the charging time.

The theoretical discharge capacity of LiCoO ₂ is 27
4 mAh / g, but when deep charge / discharge is performed, LiCoO
_{Since 2} causes a phase change to affect the cycle life, the practical discharge capacity of an actual lithium ion secondary battery is in the range of 125 to 140 mAh / g. In contrast, the theoretical discharge capacity of LiMn ₂ O ₄ is 148 mA.
h / g, this LiMn ₂ O ₄ also undergoes a phase change during charge and discharge similarly to LiCoO _2, and when a carbon-based material is used as the negative electrode active material, the irreversible capacity of the carbon-based material is large. Therefore, the discharge capacity that can be used when the battery is actually used is about 90 to 105 mAh / g. As is apparent from this, when LiMn ₂ O ₄ is used as the positive electrode active material, the battery capacity cannot be increased as compared with the case where LiCoO ₂ is used as the positive electrode active material.

Furthermore, the true density of LiCoO ₂ is 4.9 to
Whereas it is 5.1 g / cm ^3, the true density of LiMn ₂ O ₄ is 4.0~4.2g / cm ^3, considering the filling property as a positive electrode active material, towards the LiMn ₂ O ₄ Causes a disadvantage in terms of capacity.

In view of the above circumstances, the present invention provides a non-aqueous secondary battery using a lithium manganese oxide which is doped and de-doped with lithium ions by charging and discharging as a positive electrode active material, and has excellent charge load characteristics. An object of the present invention is to provide a high-capacity non-aqueous secondary battery and an appropriate method of using the same.

[0015]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, as a positive electrode active material doped with and dedoped with lithium ions, a general formula Li _x
Mn _y O _4-z , and with respect to y and z in the above formula,
0.48 ≦ y / 4−z ≦ 0.52, 0 <z ≦ 0.15, and x was restricted to a range of 0.10 ≦ x ≦ 0.95 in both the charging and discharging states. By using a spherical or elliptical spinel-type lithium manganese oxide and setting the open terminal voltage of the battery to 3 V or more, a non-aqueous secondary battery with excellent charge load characteristics and high capacity can be obtained. They have found that the problem can be solved, and have completed the present invention.

In the present invention, in the general formula representing the spinel-type lithium manganese oxide used as the positive electrode active material, x representing the amount of lithium is 0.10 ≦ x ≦ 0 in both the charge and discharge states. .95
The spinel-type lithium manganese oxide regulated to the range of the spinel-type lithium manganese oxide represented by the above general formula, in any state of charge and discharge,
This means that x is restricted and used in the range of 0.10 ≦ x ≦ 0.95.

In describing the present invention in detail, first,
First, the characteristics of the spinel-type lithium manganese oxide as a positive electrode active material for a non-aqueous secondary battery will be described. In the spinel-type lithium manganese oxide, the content ratio of the constituent elements Li, Mn, and O is determined by the electrochemical Has a large effect on the overall capacity.

Conventionally used LiMn_TwoO_FourIs the composition ratio
As is clear from the above, the average valence of Mn is 3.5.
Usually, trivalent Mn and tetravalent Mn are mixed in equal amounts.
You. However, trivalent is actually involved in charging and discharging.
Mn only, LiMn_TwoO _FourTrivalent Mn in the composition of
Increases, the discharge capacity increases. Therefore, trivalent
To increase Mn, LiMn_TwoO_FourIn the crystal structure of
Lithium manganese oxide with reduced oxygen content
Can be considered.

However, when the amount of trivalent Mn increases, Li
Mn_TwoO_FourStructure changes from cubic spinel structure to tetragonal
LiMn_TwoO_FourCauses a phase change. This tetragonal Li
Mn _TwoO_FourIs chargeable and dischargeable in the lithium potential 3V region
However, if a high potential around 4V is required, use
I can't. LiMn_TwoO_FourOxygen content in LiM
n_TwoO_FourImportant for determining the valence of Mn (manganese)
In other words, if the oxygen content is large, tetravalent Mn increases,
When the content is small, trivalent Mn increases. Trivalent Mn is
Substances that cause valence changes due to the Moon-Teller effect
LiMn itself is liable to undergo a phase change during charging and discharging._TwoO
_FourDestabilizes the structure of Li, and the inflow and out of Li (lithium) ions
As a result, the spinel phase is likely to be destroyed.

LiMn ₂ O ₄ is doped with lithium ions in the crystal structure and undoped to form LiMn ₂ O _4.
The (lithium) amount changes in the range of 0 to 1.00, and the electrochemical capacity decreases. For this reason, it is preferable that the lithium content is as high as possible. However, excess Li exceeding the stoichiometric composition is required to account for 16% of Mn in LiMn ₂ O ₄ .
d into the d site and into the Mn 16d site
Does not participate in charging and discharging. Furthermore, when Li enters the 16d site of Mn, tetravalent Mn in LiMn ₂ O ₄ increases, and the charge / discharge electric capacity decreases. Therefore, the general formula Li _x
In the spinel-type lithium manganese oxide represented by Mn _y O _4-z, the oxygen content _{O 4-z (0 <z} ≦ 0.1
5) When the ratio of Mn to O is 0.48 ≦ y / 4−
By setting z ≦ 0.52, the average valence of Mn becomes 3.5 or less, and a large amount of trivalent Mn can be contained.

If the oxygen content is too high, the tetravalent Mn increases as described above, and the charge / discharge capacity decreases, so that the oxygen content is less than 4 and 3.85 or more; That is, it is required that 0 <z ≦ 0.15.

According to the present invention, based on the above findings, first, a lithium manganese oxide is made to have a composition containing as much trivalent Mn as possible while maintaining a spinel structure, thereby increasing the discharge capacity and increasing the 4V class. Can sufficiently cope with the high potential.

Further, according to the present invention, when the above-mentioned spinel-type lithium manganese oxide is used as a positive electrode active material, x representing lithium amount is 0.10 ≦ x ≦ 0.95 in both states of charge and discharge. And by setting the open terminal voltage of the battery to 3 V or more, a non-aqueous secondary battery having excellent charge load characteristics can be obtained.

That is, originally, in order to increase the battery capacity, it is preferable to use all of the lithium in the spinel-type lithium manganese oxide as the positive electrode active material for the charge / discharge reaction. However, when the spinel-type lithium manganese oxide of the present invention is used as the positive electrode active material, the capacity that can be charged by the constant current charging method is small due to the magnitude of the polarization. For example, when the charge end voltage is set to 4.2 V, It was found that it was necessary to charge for a long time with constant voltage charging.
Therefore, in the present invention, in both the charging and discharging states, the amount of lithium in the positive electrode active material is limited to a certain range, that is, 0.10 ≦ x ≦ 0.95, and the spinel-type lithium manganese oxide is restricted. By using things,
It has been found that by increasing the capacity capable of constant-current charging and shortening the time of constant-voltage charging, excellent charging load characteristics can be obtained even at high-rate charging.

In the spinel-type lithium manganese oxide used in the present invention, the charge / discharge cycle is performed by doping / dedoping lithium in the crystal. Can be achieved by initially charging the battery so that the open terminal voltage becomes 3 V or more after assembling the battery, and controlling the termination voltage of discharging and charging so that the doped lithium remains in the negative electrode after charging.

In the present invention, based on the above reasons,
General formula Li used as a positive electrode active material _xMn_yO_4-zFilling
The values of x, y, and z during the discharge cycle are as follows:
Like

0.10 ≦ x ≦ 0.95, 0.48 ≦ y / 4−z ≦ 0.52, 0 <z ≦ 0.15

When the non-aqueous secondary battery is used, the non-aqueous secondary battery is used in a voltage range of 3 V or more, so that the non-aqueous secondary battery has excellent charge load characteristics and high capacity. The characteristic that there is can be exhibited properly.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the spinel-type lithium manganese oxide used as a positive electrode active material in the present invention will be described in detail.
Regarding ₂ O ₄ , its shape and production raw materials are mentioned. As a production raw material of LiMn ₂ O ₄ , electrolytically synthesized manganese dioxide is generally used. However, LiMn ₂ O produced using this electrolytically synthesized manganese dioxide
_As shown in the electron micrograph of FIG. 2, the _quaternary oxide has a shape with angular particles.

In order to increase the capacity of a non-aqueous secondary battery, it is necessary to increase the density of the positive electrode mixture. In the case of LiMn ₂ O ₄ in which the particles are angular as described above, however, the angularity is large. Due to the shape, the density of the positive electrode mixture cannot be increased, and the packing density of the positive electrode active material decreases.

The positive electrode of a non-aqueous secondary battery is prepared by applying a paste containing a positive electrode mixture containing a positive electrode active material and a binder to a conductive substrate and drying the paste to form a positive electrode mixture coating film on the conductive substrate. Although it is produced through a forming step, in the LiMn ₂ O ₄ particles having the angular shape as described above, the electrochemical reaction between the LiMn ₂ O ₄ particles in the coating film occurs due to the angular shape. It does not progress uniformly.

On the other hand, the spinel-type lithium manganese oxide used in the present invention has a spherical or elliptical secondary particle as shown in the electron micrograph of FIG. It is considered that the electrochemical reaction between the positive electrode active material particles progresses uniformly, whereby a large discharge capacity can be expected and a high capacity non-aqueous secondary A battery can be obtained. In the present invention, in expressing the shape of the spinel-type lithium manganese oxide, the shape is expressed as spherical or elliptical, but this is all from almost spherical to almost elliptical (that is, almost spherical to almost elliptical). (Including intermediate shapes up to an elliptical shape), which means that any shape included therein may be used.

The particle diameter of the spinel-type lithium manganese oxide used in the present invention is preferably from 1 to 45 μm, more preferably from 1 to 25 μm in average particle diameter, in order to enhance the charge / discharge efficiency. The specific surface area is 0.5 to ³ m ^{2 in} order to increase the effective reaction area.
/ G is preferable, and particularly preferably 1 to ³ m ² / g. By setting such average particle diameter and specific surface area, the progress of the electrochemical reaction becomes smooth and the charge / discharge capacity is improved. I found that I can do it.

The spinel-type lithium manganese oxide used in the present invention has an average particle diameter of 1 to 45 μm,
The reason why the charge / discharge capacity can be improved by setting the specific surface area to 0.5 to 3 m ² / g is not necessarily clear at present, but is considered as follows. That is, the positive electrode of the nonaqueous secondary battery of the present invention is obtained by dispersing the spinel-type lithium manganese oxide in a solvent using a binder or the like to form a paste, and using the positive electrode mixture-containing paste as a current collector. Coated on a conductive substrate and dried to form a positive electrode mixture coating film on the conductive substrate. The average particle size of the spinel-type lithium manganese oxide during preparation of this positive electrode mixture-containing paste Diameter of 1μm or more, specific surface area of 3
By setting the ratio to m ² / g or less, the aggregation of the spinel-type lithium manganese oxide particles in the positive electrode mixture-containing paste can be suppressed, and the wettability of the spinel-type lithium manganese oxide particles to the solvent is improved. Therefore, the amount of the solvent used in preparing the paste can be reduced. If the solvent is left in the positive electrode mixture coating film formed by applying the positive electrode mixture-containing paste on a conductive substrate and drying the solvent, the solvent adversely affects the load characteristics. As described above, the amount of solvent used can be reduced as described above, so that the residual solvent in this positive electrode mixture coating film can be reduced, and in addition, the conductive property which affects the battery characteristics during the positive electrode preparation process is reduced. Since the drying temperature of the positive electrode mixture-containing paste applied on the substrate can be reduced, the spinel-type lithium manganese oxide, binder, electron conduction aid, etc. in the positive electrode mixture-containing coating film after drying of the positive electrode mixture-containing paste Are considered to be uniform, and these are also factors that improve the load characteristics.

On the other hand, the average particle diameter of the spinel type lithium manganese oxide is 45 μm or less, and the specific surface area is 0.4 μm.
By setting it to 5 m ² / g or more, the progress of the electrochemical reaction on the surface of the particles is smoothed, and the particles become spinel-type lithium manganese oxide, so that the density of the positive electrode mixture coating film is further increased. Thus, the effect of the spherical or elliptical particle shape of the present invention can be more remarkably exhibited. In the present invention, the average particle diameter is a value obtained by measuring the particle diameter of each particle in an electron micrograph (magnification: 500 times) and obtaining the average value of the particle diameters of 50 particles, The specific surface area is 12
Degassed at 0 ° C for 20 hours.
After the pressure becomes 0 mTorr or less, the pores of 1 to 100 ° of the sample are measured by a nitrogen adsorption method (manufactured by Yuasa Ionics, Auto Soap 1), and the value obtained from the measured value on the adsorption side at that time is referred to.

The spinel-type lithium manganese oxide of the present invention preferably has a Fe (iron) content of 200 ppm or less. That is, transition metals other than manganese are mixed in the production process of the chemically synthesized manganese dioxide which is a raw material of the spinel-type lithium manganese oxide of the present invention. It has been found that when a spinel-type lithium manganese oxide is synthesized using manganese dioxide as a raw material, the charge / discharge capacity of the product can be improved, and a nonaqueous secondary battery having excellent load characteristics can be obtained. Although the reason for this is not always clear at present, the present inventors have considered that, when manganese dioxide containing Fe is used, iron oxide or Fe-containing lithium which does not contribute to the charge / discharge reaction in the production process of lithium manganese oxide is considered. It is believed that oxides are formed. Therefore, by using manganese dioxide having a small Fe content, the generation of the above-described impurities is suppressed, and the Fe content in the lithium manganese oxide is controlled to 200 ppm or less, thereby performing doping / de-doping by charge / discharge reaction. It is considered that the efficiency of lithium ion diffusion in the solid phase can be increased, and not only the charge / discharge capacity but also the load characteristics can be improved.

In order to synthesize one equivalent of spinel-type lithium manganese oxide, manganese dioxide as a raw material must
Since an equivalent amount is necessary, the Fe component, which is an impurity in manganese dioxide, is contained in lithium manganese oxide in about 2%.
It is concentrated to twice the content. Therefore, it is considered that the content of the Fe component in the manganese dioxide has a great influence on the load characteristics of the obtained spinel-type lithium manganese oxide.

Based on the above findings, the present inventors have determined that the Fe content in the spinel-type lithium manganese oxide is 200 p.
pm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less so that when the spinel-type lithium manganese oxide is used as a positive electrode active material, a high charge / discharge capacity and excellent load characteristics can be obtained. It was done.

Next, a method for synthesizing the spinel-type lithium manganese oxide used in the present invention will be described. As a manganese source, chemically synthesized manganese dioxide is used, and in this case, it is preferable to use a spherical or elliptical one. . By using the spherical or elliptical chemically synthesized manganese dioxide, the obtained spinel-type lithium manganese oxide can be easily formed into a spherical or elliptical shape. Further, in order to produce a spinel-type lithium manganese oxide having the above particle diameter and specific surface area, it is preferable to use a manganese dioxide having an average particle diameter of 1 to 45 μm, particularly an average particle diameter. 1-2
It is preferable to use one having a size of 5 μm.

In order to reduce the Fe content in the spinel type lithium manganese oxide to 200 ppm or less, F
It is preferable to use chemically synthesized manganese dioxide having a low e content.

The chemically synthesized manganese dioxide having a low Fe content as described above can be produced by a conventionally known method. For example, in the process of dissolving manganese as an ion in an aqueous solution in the production process of chemically synthesized manganese dioxide, the addition of calcium carbonate or the like or the sulfidation of
When precipitating the component as a salt, a chemically synthesized manganese dioxide having a small Fe content can be produced by adjusting the pH and the amount of addition in the solution. Also, in the process of precipitating manganese ions with ammonium carbonate or the like and extracting it as manganese carbonate, if the pH or the amount of addition in the solution is not sufficiently adjusted, the Fe component may precipitate at the same time. Therefore, by adjusting the amount of ammonium carbonate or the like and the pH of the solution,
Manganese dioxide having a low Fe content can be produced.

The lithium source to be reacted with the manganese dioxide is not particularly limited, and various lithium salts can be used. For example, lithium hydroxide / monohydrate, lithium nitrate, lithium carbonate, lithium acetate ,
Lithium bromide, lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide, etc. Lithium hydroxide monohydrate is particularly preferred because it does not generate gases that adversely affect the environment, such as nitrogen oxides and sulfur oxides. Then, a spinel-type lithium manganese oxide is obtained by mixing such a lithium salt with the manganese dioxide and firing the mixture.
At that time, part of Mn was Al for improving cycle characteristics.
Other elements such as Cu, Fe, Ni, Co, Cr, B, and Si can be substituted. At this time, the solid solution amount (b) of the other element (the other element is represented by A) is represented by the general formula Li _x (Mn
_{1-b Ab} ) _y O _4-z (x,
The values of y and z are 0.10 ≦ x ≦ 0.95, 0.48 ≦ y
/4−z≦0.52, 0 <z ≦ 0.15, and A is A
1, at least one of Cu, Fe, Ni, Co, Cr, B, and Si) in the range of 0 <b ≦ 0.1. By replacing part of the manganese element with another element, the bonding strength between oxygen and manganese atoms in the spinel structure increases, and the crystal structure is stabilized,
The above-mentioned other element solid solution spinel type lithium manganese oxide is preferable in terms of improving the cycle characteristics of the battery, particularly the high-temperature cycle characteristics. In general other element solid solution spinel type lithium manganese oxide, the discharge capacity decreases because the solid solution element does not normally participate in charge / discharge, but in the other element solid solution spinel type lithium manganese oxide of the present invention, the range of x By controlling, the decrease in the discharge capacity can be suppressed, and it can be suitably used as a positive electrode active material. And
In the other element solid-solution spinel lithium manganese oxide represented by the general formula Li _x (Mn _{1-b Ab} ) _y O _4-z , The Fe content is preferably 200 ppm or less, the specific surface area of the other element solid solution spinel type lithium manganese oxide is preferably 0.5 to ³ m ² / g, and the average particle diameter is 1 to 45 μm. Preferably, there is.

In the production of the spinel type lithium manganese oxide used in the present invention, the charging ratio of manganese dioxide and lithium salt is Li by mixing molar ratio of Li and Mn.
/Mn≦0.5, especially 0.45 ≦ Li / Mn ≦ 0.49
Is preferable. It is preferable that the mixing molar ratio of Li and Mn is set to 0.5 or less because of the Li / Mn.
When the mixing molar ratio of Mn is larger than 0.5, reaction intermediate products and the like tend to remain, and the intermediate products hinder the charge / discharge reaction in the battery system, thereby reducing the charge / discharge capacity of the non-aqueous secondary battery. This is because there is a possibility that the size may be reduced.

In the production of the spinel-type lithium manganese oxide, it is preferable that manganese dioxide and a lithium salt are mixed and pelletized and then fired. That is, since the reaction proceeds by solid-phase diffusion of the raw material in order to carry out the reaction in a solid-phase reaction, the pelletization improves the contact between the lithium salt particles of the raw material and the manganese dioxide particles, and the reaction proceeds. It will be easier to progress. The size of the pellet is preferably 5 to 15 mm in its longest diameter.

In the production of the spinel-type lithium manganese oxide used in the present invention, the firing conditions are as follows: the temperature is raised to 780 to 820 ° C .;
It is preferable to hold for ~ 36 hours. 780-820 ° C
By baking, the crystallinity of the generated lithium manganese oxide is improved, and a spinel-type manganese structure is easily formed. When the firing temperature is lower than 780 ° C or lower,
When the firing temperature is higher than 820 ° C., the difference between the charge capacity and the discharge capacity of the spinel-type lithium manganese oxide, that is, irreversible, is obtained when the crystallinity of the spinel-type lithium manganese oxide and the generation of impurities decrease the discharge capacity. The capacity may increase and the discharge capacity may decrease.

As the heat treatment for the above firing,
It is preferable to preheat from room temperature to 250 to 500 ° C., which is the melting point of the lithium salt, and then raise the temperature to 780 to 820 ° C., rather than raising the temperature to 780 to 820 ° C. at once. This is because the reaction between the lithium salt and manganese dioxide occurs stepwise, and the spinel-type lithium manganese oxide is generated via the intermediate product. It is for preheating, and when the temperature is raised to 780 to 820 ° C at a stretch,
The lithium salt and manganese dioxide partially react to the final stage, and the resulting spinel-type lithium manganese oxide may hinder the reaction of unreacted substances.
It is also effective to carry out heating stepwise in order to shorten the firing time for obtaining the desired spinel-type lithium manganese oxide. The preheating time is not particularly limited, but is usually preferably 12 to 30 hours, and it is preferable that the temperature be raised from room temperature to around the melting point of the lithium salt, and that the temperature be maintained before heating.

The atmosphere for the heat treatment including the above-mentioned baking and preheating is preferably performed in a mixed atmosphere of an inert gas such as argon, helium and nitrogen and an oxygen gas.
The mixing ratio of these gases is preferably in the range of 5/5 to 9/1 by volume ratio of inert gas / oxygen gas, and more preferably in the range of 8/2 to 9/1.
As described above, the inert gas / oxygen gas is 5/5 by volume ratio.
By setting the ratio to 9/1, the progress of the reaction is facilitated, and a spinel-type lithium manganese oxide containing no impurities can be easily obtained.

The flow rate of the mixed gas of the inert gas and the oxygen gas is preferably 1 liter / minute or more per 100 g of the starting material mixture, and more preferably 1 to 5 liter / minute per 100 g of the material mixture. When the gas flow rate is small, that is, when the gas flow rate is low, a difference occurs in reactivity to the spinel structure, and Mn ₂ O ₃ or Li ₂ MnO
There is a possibility that impurities such as ₃ may remain.

In the present invention, in order to produce a positive electrode, for example, the above-mentioned spinel-type lithium manganese oxide, if necessary, an electron conduction aid such as flake graphite, acetylene black, etc. Ethylene, a binder such as polyvinylidene fluoride is added and mixed, and the obtained positive electrode mixture is, for example, pressure-formed or
Alternatively, a positive electrode mixture-containing paste is prepared by dispersing in an organic solvent (in this case, the binder may be dissolved in an organic solvent in advance and then mixed with a positive electrode active material such as spinel-type lithium manganese oxide). The positive electrode mixture-containing paste is applied to a conductive substrate and dried to form a positive electrode mixture coating film on the conductive substrate. Explaining the positive electrode mixture coating film, volatile components such as a solvent in the positive electrode mixture-containing paste applied to the conductive substrate evaporate in a drying step for forming the coating film, and the positive electrode formed on the conductive substrate The mixture coating film is composed of a positive electrode mixture composed of a mixture of a spinel-type lithium manganese oxide as a positive electrode active material and a binder or an electron conduction aid added as necessary.

The organic solvent used for preparing the paste containing the positive electrode mixture is, for example, N-methyl-2.
-Pyrrolidone (hereinafter abbreviated as "NMP"), ethyl methyl ketone, isobutyl methyl ketone, cyclohexanone, toluene, tetrahydrofuran and the like, which are appropriately selected and used.

As the active material of the negative electrode opposed to the positive electrode, lithium or a lithium-containing compound is used. As the lithium-containing compound, there are a lithium alloy and other compounds. Examples of the lithium alloy include lithium-aluminum, lithium-lead, lithium-indium, lithium-gallium, lithium-indium-gallium, and the like. Examples of the lithium-containing compound other than the lithium alloy include tin oxide, silicon oxide, nickel-silicon alloy, magnesium-silicon alloy, carbon material having a turbostratic structure, graphite, tungsten oxide, and lithium iron composite. Oxides and the like.
Some of these exemplified lithium-containing compounds do not contain lithium at the time of manufacture, but when they act as a negative electrode active material, they contain lithium. Of these, in particular, when a carbon-based material, graphite, or the like is used as the negative electrode active material, lithium ions doped from the spinel-type lithium manganese oxide by the first charge remain in the negative electrode active material as lithium for an irreversible capacity, It is easy to control the amount of lithium in the spinel-type lithium manganese oxide during charge and discharge.

The negative electrode is mixed with the above-mentioned negative electrode active material, if necessary, by adding the same binder and electron conduction assistant as in the case of the above-mentioned positive electrode active material, and molding the obtained negative electrode mixture by an appropriate means. It is produced by doing. For example, the negative electrode mixture is press-molded, or the negative electrode mixture is dispersed in the same organic solvent as used for the positive electrode to prepare a negative electrode mixture-containing paste (in this case, the binder is an organic solvent or the like in advance. And then mixed with the negative electrode active material, etc.), and applying the negative electrode mixture paste to a conductive substrate, drying and forming a negative electrode mixture coating film on the conductive substrate Produced by

As a method of applying the above-mentioned paste containing the positive electrode mixture and the paste containing the negative electrode mixture to the conductive substrate, for example, various coating methods such as an extrusion coater, a reverse roller, a doctor blade and the like are employed. be able to. Examples of the conductive substrate for the electrodes such as the positive electrode and the negative electrode include metal meshes such as aluminum, stainless steel, titanium, and copper, punched metal, expanded metal, foam metal, and foil. , An aluminum foil is particularly suitable as the conductive substrate of the positive electrode, and a copper foil is particularly suitable as the conductive substrate of the negative electrode.

The ratio of the amount of active material in the positive electrode and the amount of active material in the negative electrode depends on the type of the active material and the like, but it is preferable that the ratio of positive electrode active material / negative electrode active material = 1.5 to 4.0 (weight ratio). .

In the non-aqueous secondary battery using the spinel-type lithium manganese oxide of the present invention as a positive electrode active material, the electrolyte is usually a non-aqueous liquid electrolyte (hereinafter, referred to as a “liquid electrolyte” in which a lithium salt is dissolved in an organic solvent). Electrolyte ") is used. The solvent of the electrolytic solution is not particularly limited, but it is particularly suitable to use a chain ester as a main solvent. Examples of such a chain ester include diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EM
C), ethyl acetate (EA), methyl propionate (M
Organic solvents having a chain COO-bond such as P). The fact that these chain esters are the main solvent of the electrolyte means that these chain esters are 5% of the total electrolyte solvent.
It means that the chain ester occupies more than 0% by volume, especially the chain ester occupies 65% by volume or more in the total electrolyte solution solvent, and especially the chain ester occupies 70% by volume or more in the total electrolyte solution solvent. Preferably, the chain ester accounts for 75% by volume or more of the total electrolyte solution solvent.

It is preferable that the chain ester be used as the main solvent as the solvent of the electrolyte because the chain ester exceeds 50% by volume in the total solvent of the electrolyte. Is improved.

However, in order to improve the battery capacity, an ester having a high dielectric constant (dielectric constant of 30 or more) is used as the electrolyte solvent instead of using the chain ester alone as the electrolyte solvent. Are preferably used in combination. The amount of the ester having such a high dielectric constant in the total electrolyte solvent is preferably at least 10% by volume, particularly preferably at least 20% by volume. That is, when the amount of the ester having a high dielectric constant is 10% by volume or more in the total electrolyte solvent, the improvement in capacity is clearly exhibited, and when the amount of the ester having a high dielectric constant becomes 20% by volume or more in the total electrolyte solution. The improvement in capacity is more clearly expressed. However, if the volume of the ester having a high dielectric constant in the total electrolyte solvent is too large, the discharge characteristics of the battery tend to decrease. , As described above, preferably within a range of 10% by volume or more, more preferably 20% by volume or more.
It is preferably 0% by volume or less, more preferably 30% by volume or less, and further preferably 25% by volume or less.

Examples of the ester having a high dielectric constant include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and γ-
Butyrolactone (γ-BL), ethylene glycol sulphite (EGS) and the like are preferable, and those having a cyclic structure such as ethylene carbonate and propylene carbonate are preferable, and cyclic carbonate is particularly preferable. Specifically, ethylene carbonate (EC) is preferable. Is most preferred.

Examples of the solvent that can be used in combination with the ester having a high dielectric constant include, for example, 1,2-dimethoxyethane (1,2-DME) and 1,3-dioxolane (1,2).
3-DO), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2-Me-THF), diethyl ether (DEE) and the like. In addition, an amine-based or imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, and the like can also be used.

As the solute of the electrolytic solution, for example, LiCl
O_Four, LiPF₆, LiBF_Four, LiAsF₆, LiS
bF₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, Li
CF _ThreeCO_Two, Li_TwoC_TwoF_Four(SO_Three)_Two, LiN
(CF_ThreeSO_Two)_Two, LiC (CF_ThreeSO_Two)_Three, Li
C_nF_{2n + 1}SO_Three(N ≧ 2) alone or two or more
The above mixture is used. Especially LiPF₆And LiC_FourF₉
SO_ThreeAnd the like are preferable because of good charge / discharge characteristics. Electric
The concentration of solute in the lysate is not particularly limited.
But not 0.3 to 1.7 mol / l, especially 0.4 to 1.
About 5 mol / l is preferable.

In the present invention, a gel electrolyte, a solid electrolyte, or the like can be used in addition to the above-mentioned electrolyte. Examples of the gel electrolyte and solid electrolyte include inorganic electrolytes, polyethylene oxide, polypropylene oxide, epoxy resin, polyacrylonitrile, urethane resin, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride. -An organic electrolyte containing a tetrafluoroethylene copolymer or a derivative thereof as a main material, and the like.

As the separator, a separator having sufficient strength and capable of holding a large amount of electrolyte is preferable. From such a viewpoint, the thickness is 10 to 50 μm and the porosity is 30 to 70 μm.
% Of polypropylene, polyethylene or a copolymer of ethylene and propylene.

In the non-aqueous secondary battery of the present invention, for example, an electrode body obtained by winding or laminating the above positive electrode and negative electrode via a separator is inserted into a battery case, and an electrolyte is injected into the battery case and sealed. Assembled by

When the nonaqueous secondary battery is used at an open terminal voltage of 3 V or more, lithium in the spinel-type lithium manganese oxide is dedoped as lithium ions at the first charge, and this is doped into the negative electrode active material. By doing so, a charge / discharge cycle is performed. The present invention, during the charging and discharging, in both the charging and discharging is also a general formula Li _x Mn _y O _4-z lithium content x in, 0.10 ≦ x
By regulating to ≦ 0.95, the charging load characteristics are improved.

That is, the lithium ions in the spinel-type lithium manganese oxide during charge / discharge are LiCo
Instead of moving in the gap between the layers of oxygen as in the case of O ₂ or LiNiO ₂ , it must move in the solid phase of lithium, manganese, and oxygen of the spinel-type lithium manganese compound. Therefore, lithium ions must move between sites where lithium, manganese, and oxygen are present in the spinel-type lithium manganese compound, and the movement of lithium ions in the crystal becomes extremely slow. As a result, the spinel-type lithium manganese oxide has a lower diffusion rate of lithium ions in the crystal than LiCoO _{2 and the} like, and has a large polarization at the time of constant current charging. It is thought to be. In addition, in non-aqueous secondary batteries, the positive electrode active material usually has a slower diffusion rate of lithium ions than the negative electrode active material, and the diffusion rate of lithium ions is positive electrode rate-determining. It is necessary to use the cathode active material at a high diffusion rate.

Regarding the amount of lithium in the crystal during charging and discharging, the spinel-type lithium manganese oxide used in the present invention has a composition with a large amount of lithium. In addition, when the lithium ions move in the solid phase, the repulsion of the lithium ions interferes with each other, which makes it difficult for the lithium ions to move freely and makes it difficult to flow a sufficient current. On the other hand, as the lithium content of spinel-type lithium manganese oxide decreases, LiCo
Since there is no oxygen-oxygen layer such as O ₂ and LiNiO ₂ , the lithium ion content in the crystal is reduced and its lattice volume is reduced, and as a result, the distance between the constituent elements is reduced, so that lithium and manganese are reduced. As a result, it becomes difficult to flow a current sufficiently as in the case where the ion content is large, and the charging load characteristics are degraded. Furthermore, since the spinel-type lithium manganese oxide used in the present invention contains a large amount of trivalent Mn by lowering the oxygen content,
Doping and undoping of lithium from the spinel-type lithium manganese oxide due to the Jahn-Teller effect caused by this causes the crystal structure to be unstable and the spinel phase to be easily broken.

It is originally desirable to increase the battery capacity by undoping / doping a large amount of lithium during charge and discharge. However, the battery using the spinel-type lithium manganese oxide of the present invention as a positive electrode active material has improved charge load characteristics. In order to achieve this, the amount x of lithium in the spinel-type lithium manganese compound is 0.10 or more, preferably 0.15
And more preferably 0.20 or more, and the lithium amount x at the time of discharge is 0.95 or less, preferably 0.93 or less.
More preferably, by setting it to 0.90 or less, the charging time required for constant voltage charging can be shortened, and the charging load characteristics can be improved. That is, by setting the lithium amount x in the crystal at the time of discharging to 0.95 or less, repulsion of lithium ions in the crystal can be reduced, and by setting the lithium amount x to 0.10 or more at the time of charging, lithium from the crystal can be reduced. The reason is that a passage for ions to be undoped is secured to improve the diffusion rate, and the stability of the crystal structure is maintained, so that excellent charge load characteristics and discharge capacity can be secured.

As a method of regulating the amount of lithium, the nonaqueous secondary battery of the present invention is assembled in a discharged state. Lithium ions are doped from the active material spinel-type lithium manganese oxide, and a part of the doped lithium ions is left in the negative electrode at the time of subsequent charge / discharge. By terminating it, it is possible to regulate the amount of lithium. The end voltage varies depending on the type of the negative electrode active material. For example, when graphite is used as the negative electrode active material, the charge end voltage is 4.1 to 4.3 V, and the carbon-based material having a turbostratic structure is used as the negative electrode active material. 4.2 to 4.3 when used as a substance
V and any of the carbon-based materials can be regulated by setting the discharge end voltage to 3.0 V or more. In addition, it is preferable that the charging be performed at a constant current and a constant voltage.
To reduce the charging time, the charging current is 2.5 mA / c
It is preferable to perform charging at a current density of m ² or less.

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. However, the present invention is not limited to only these examples.

Example 1 Spherically shaped chemically synthesized manganese dioxide (the Fe content in this chemically synthesized manganese dioxide was 21 ppm) was previously classified to 45 μm or less. Further, granular lithium hydroxide monohydrate as a lithium source was ground by a planetary ball mill until it became fine powder. Next, 19.23 g of the above-mentioned chemically synthesized manganese dioxide and 4.36 g of lithium hydroxide monohydrate were mixed, and further sufficiently pulverized and mixed in a planetary ball mill. The mixture was compression-molded into pellets using a press machine, and the pellets were placed in an alumina boat and fired in a tubular electric furnace. The molar ratio Li / Mn between the amount of Mn in the above chemically synthesized manganese dioxide and the amount of Li in lithium hydroxide monohydrate is 0.47.
Met.

The firing atmosphere was argon gas / oxygen gas =
8/2 (volume ratio) of the mixed gas was mixed with the raw material mixture (ie,
The mixture was supplied at a flow rate of 1.0 liter / minute per 100 g of a mixture of a chemically synthesized manganese dioxide as a starting material and lithium hydroxide / monohydrate. Firing is first 200
The temperature was raised to 470 ° C. at a rate of ° C./h, the temperature was maintained at 470 ° C. for 24 hours to perform preheating, and then the temperature was raised to a rate of 800 ° C. at a rate of 100 ° C./h, and the temperature was maintained at 800 ° C. for 36 hours. After that, natural cooling is performed, and the temperature of the fired product is 80 ° C.
After the temperature became below, the fired product was taken out of the tubular electric furnace and sufficiently pulverized.

After the fired product was sufficiently pulverized and mixed as described above, it was compression-molded again into pellets, and the pellets were fired in the same manner as described above. That is, the temperature was raised to 800 ° C. at a temperature rising rate of 200 ° C./h, and firing was performed at a temperature of 800 ° C. for 36 hours. Thereafter, the temperature was allowed to cool to room temperature by natural cooling, and after the temperature was lowered, the pellet was sufficiently pulverized, and the pulverized powder was classified to obtain a spherical or elliptical powder of 45 μm or less. Magnification 15 of the particle structure of this lithium manganese oxide
A 10 × electron micrograph is shown in FIG. In FIG.
The portion which looks whitish is the lithium manganese oxide, but as shown in FIG. 1, the obtained lithium manganese oxide was spherical or elliptical.

[0073] In order to lithium manganese oxide obtained is confirmed to be a spinel structure, where lithium manganese oxide obtained was analyzed by X-ray diffraction, specific to LiMn ₂ O ₄ having a spinel structure Since a diffraction line was observed and no peak due to impurities was observed, it was confirmed that the obtained lithium manganese oxide was a lithium manganese oxide having a spinel structure.

Further, the composition of Li, Mn and O in the obtained lithium manganese oxide was measured by an atomic absorption spectrometer. In this measurement, a sample was prepared as follows. That is, the obtained lithium manganese oxide 0.2
10 ml of ion-exchanged water and 10 ml of 12N hydrochloric acid were added to 5 g, and the mixture was heated until lithium manganese oxide was completely dissolved. Then, let it cool down to room temperature, add ion exchange water,
The total amount was adjusted to 100 ml to prepare a sample for analysis. The analysis of each element was performed by the standard addition method. From the analysis results, the composition of the obtained lithium manganese oxide was Li _1.01 Mn _1.99 O
It turned out to be _3.88 . Further, when the Fe content in the lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in the composition analysis of Li, Mn, and O, the Fe content was 40 ppm.

The average particle size of the particles is determined by an electron micrograph (magnification: magnification) of the obtained spinel-type lithium manganese oxide.
500 times), the particle diameter of each particle in the photograph was measured, and the average value of the particle diameters of 50 particles was determined. The average particle diameter was 25 μm. In addition, the specific surface area was degassed at 120 ° C. for 20 hours by using Yuasa Ionics' Autosorb-1 with the measurement range of the sample pores being 1 to 100 °, and the measurement environment vacuum degree of the sample became 10 mTorr or less. After confirming this, measurement was performed using nitrogen gas as a probe gas, and the specific surface area was 1.0 m ² / g.

A model cell was prepared using the spinel-type lithium manganese oxide produced by the above method. First,
1.6 g of the spinel-type lithium manganese oxide, 0.3 g of acetylene black and 0.1 g of polytetrafluoroethylene were weighed out and mixed well in a mortar. These mixtures were thoroughly ground in a mortar until they became gummy, and the gummy mixture was pressed into a 500 μm mesh sieve to form a powder. 40m of this powder
g, and compression molded with a press machine together with a platinum net having a diameter of 10 mm to produce a pellet-shaped electrode.

The pellet-shaped electrode prepared as described above was used as a working electrode, and lithium foil was used as a counter electrode and a reference electrode.
A non-aqueous solution in which PF ₆ was dissolved at a concentration of 1.0 mol / l in a mixed solvent of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 1: 3 was used as an electrolyte to prepare a model cell. Thereafter, pre-charging was performed at a current density of 0.5 mA / cm ^{2 so} that the amount x of lithium became x = 0.90, and the battery was left for 48 hours. The open-circuit terminal voltage was measured. Was. Further, thereafter, the battery was subjected to a charge / discharge test such that the amount x of lithium during charge / discharge was 0.20 ≦ x ≦ 0.90 (the amount of lithium contributing to the charge / discharge reaction was 0.70).

Example 2 A chemically synthesized manganese dioxide having a spherical shape (the Fe content in the chemically synthesized manganese dioxide is 35 ppm) was previously classified to 45 μm or less. Granular lithium hydroxide monohydrate and diboron trioxide, which are lithium sources, were each pulverized by a planetary ball mill until they became fine powder.

Next, the above chemically synthesized manganese dioxide 1
9.50 g, 0.20 g of diboron trioxide and 4.64 g of lithium hydroxide monohydrate were mixed, and further sufficiently pulverized and mixed by a planetary ball mill. The obtained mixture was compression-molded into pellets by a press machine, and the pellets were placed in an alumina boat and fired in a tubular electric furnace. Mn + B in the above chemically synthesized manganese dioxide and diboron trioxide
Ratio L between the amount of Li and the amount of Li in lithium hydroxide monohydrate
i / (Mn + B) was 0.48.

The subsequent sintering and pulverizing operations were carried out at a sintering temperature of 81
A spinel-type lithium manganese oxide dissolved in another element was manufactured in the same manner as in Example 1 except that the temperature was set to 0 ° C.

Oxidation of Lithium Manganese in Solid Solution Obtained
When the product was observed with an electron microscope in the same manner as in Example 1, the shape was observed.
The shape was spherical or oval. In addition, solid solution of other elements
X-ray diffraction analysis of spinel-type lithium manganese oxide
Analysis confirmed that the lithium
It was confirmed to be a cancer oxide. Also, with the first embodiment
Similarly, the composition of Li, Mn, B, and O and the Fe content were determined by atomic absorption.
As a result of measurement with an optical analyzer,
The composition of the flannel type lithium manganese oxide is Li_{1. 03}Mn
_1.92B_0.05O_3.93And the Fe content is 72 ppm.
Was. In addition, other element solid solution spinel type lithium man
The average particle diameter and specific surface area of the gun oxide were determined in the same manner as in Example 1.
Upon measurement, the average particle size was 23 μm, and the specific surface area was
1.0m^Two/ G.

A model cell and a battery were fabricated in the same manner as in Example 1 using the spinel-type lithium manganese oxide dissolved in another element produced as described above. For the model cell,
At a current density of 0.5 mA / cm ^2, the amount x of lithium is x =
The battery was precharged to 0.94 and left for 48 hours, and then the open terminal voltage was measured. Thereafter, except that the amount x of lithium during charging and discharging was set to 0.24 ≦ x ≦ 0.94 (the amount of lithium contributing to the charging / discharging reaction was 0.70), in the same manner as in Example 1. It was subjected to a charge / discharge test.

Comparative Example 1 A model cell and a battery were prepared in the same manner as in Example 1 except that a commercially available LiMn ₂ O ₄ (average particle diameter 31 μm, specific surface area 0.8 m ² / g) was used as a positive electrode active material. . However,
In use, the range of change in the amount of lithium during charge and discharge of LiMn ₂ O ₄ , which is one type of the spinel-type lithium manganese oxide, was set to 0.05 to 0.75. When the commercially available LiMn ₂ O ₄ was observed with an electron microscope in the same manner as in Example 1, the shape was angular as shown in FIG. 2 (electron micrograph at 1500 × magnification). Further, when the Fe content of this LiMn ₂ O ₄ was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 600 ppm.

A model cell was prepared in the same manner as in Example 1 using the above-mentioned LiMn ₂ O ₄ , and was precharged at a current density of 0.5 mA / cm ² so that the amount x of lithium became x = 0.75. After leaving for 48 hours, the open terminal voltage was measured. Then, the lithium amount x during charge and discharge is 0.05 ≦
A charge / discharge test was performed in the same manner as in Example 1 except that x ≦ 0.75 (the amount of lithium contributing to the charge / discharge reaction was 0.70).

Comparative Example 2 In Example 1, F in the chemically synthesized manganese dioxide as a raw material was used.
e, a chemically synthesized manganese dioxide having a content of 329 ppm was used, and the molar ratio of the Mn content in the chemically synthesized manganese dioxide to the Li content in lithium hydroxide monohydrate was 0.52.
The raw materials are mixed so as to be 5 and the firing temperature is 85.
A lithium manganese oxide was produced in the same manner as in Example 1, except that the temperature was changed to 0 ° C. and the product was not classified. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed to be a spinel-type lithium manganese oxide. Also, as in Example 1, Li,
When the composition of Mn and O and the Fe content were measured by an atomic absorption spectrometer, the composition of the produced lithium manganese oxide was Li _1.08 Mn _1.92 O _3.96 , and the Fe content was 643.
ppm. Further, when the average particle diameter and the specific surface area of this lithium manganese oxide were measured in the same manner as in Example 1, the average particle diameter was 62 μm and the specific surface area was 0.1 m ^2.
/ G.

The spinel-type lithium produced as described above
Using a manganese oxide and a model cell as in Example 1
A battery was manufactured. For the model cell, 0.5 mA /
cm ^TwoThe lithium amount x becomes x = 0.98 at the current density of
After pre-charging and leaving for 48 hours,
The voltage was measured. Then, the amount of lithium at the time of charging and discharging x
Is 0.28 ≦ x ≦ 0.98 (Lithium that contributes to the charge-discharge reaction
Except that the amount of um is 0.70)
A charge / discharge test was performed in the same manner as in Example 1.

Examples 1 and 2 produced as described above
The charge load characteristics, discharge capacity and discharge load characteristics of the model cells of Comparative Examples 1 and 2 were examined. Table 1 shows the results. The method of measuring the charge load characteristics, discharge capacity, and discharge load characteristics is as follows.

Charging load characteristics: Constant current charging was started at a current density of ^2.5 mA / cm ² , and the amount of electricity per unit weight of the positive electrode active material was 65 mAh / g (x is x =
(Equivalent to 0.44 minutes), the constant-current charging is terminated at the time of charging, and then the constant-voltage charging is performed.
The charging load characteristics were evaluated by measuring the time taken to charge an electric quantity of 0.36 minutes. Therefore, in displaying the evaluation result of the charging load characteristic in Table 1, the time required for charging the above-mentioned electric quantity by constant voltage charging (constant voltage charging time) is displayed.

Discharge capacity: The model cell in which the charge load characteristic was measured was measured at a current density of ^2.5 mA / cm ² , and the final voltage was defined as the open terminal voltage measured before the start of the charge load characteristic test.
The discharge capacity at the time of discharging was measured, and the measured value was converted into the discharge capacity per unit weight of the positive electrode active material.

Discharge load characteristics: Model after discharge capacity measurement
After leaving the cell for 48 hours, 0.5 mA / cm^TwoNo electricity
Open terminal voltage measured before charging load characteristic test at current density
, And constant voltage discharge was performed for 36 hours. So
After 48 hours, measure the open terminal voltage and charge negative.
± 0.01V difference from open terminal voltage before starting load characteristic test
After confirming that the
0.7 mA / cm after charging with electricity and constant voltage^TwoCurrent
The discharge was performed to the open terminal voltage shown in Table 1 at the density.
2.5 mA / cm as in the above discharge capacity measurement.^Twoof
Ratio to discharge capacity when discharging at current density
[(0.7 mA / cm^TwoDischarge capacity at) / (2.5 mA
/ Cm ^TwoDischarge capacity) × 100], and the discharge load
The properties were evaluated.

[0091]

[Table 1]

In the above model cells, the amount of lithium contributing to the charging / discharging reaction in each of Examples 1 and 2 and Comparative Examples 1 and 2 was 0.70. Has a shorter constant voltage charging time during charging and is superior in charging load characteristics as compared with Comparative Examples 1 and 2. Further, Examples 1 and 2 had a larger discharge capacity than Comparative Examples 1 and 2,
The capacity was high, and the discharge load characteristics were also excellent.

[0093]

As described above, according to the present invention, the positive electrode
As an active material, the general formula Li_xMn_yO _4-zRepresented by
With respect to y and z in the formula, 0.48 ≦ y / 4−z ≦ 0.
52, 0 <z ≦ 0.15, and for x, charging and
0.10 ≦ x ≦ 0.9
Spinel-type lithium manganese oxidation regulated within 5
Use an object and make the open terminal voltage of the battery 3 V or more.
With this, non-aqueous secondary with excellent charging load characteristics and high capacity
Battery could be provided.

Further, the spinel-type lithium manganese oxide of the present invention is spherical or elliptical particles,
Since manganese, which has good load characteristics and is abundant and inexpensive as a constituent element, is suitable for mass production, its industrial significance is great.

[Brief description of the drawings]

FIG. 1 is a magnification of 15 showing the particle structure of a spinel-type lithium manganese oxide used as a positive electrode active material in the present invention.
It is a 10 times electron microscope photograph.

FIG. 2: Magnification 1 showing the particle structure of commercially available LiMn ₂ O ₄
It is a 500 times electron microscope photograph.

FIG. 3 is a partial cross-sectional perspective view schematically illustrating an example of a non-aqueous secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Insulator 6 Insulator 7 Insulation packing 8 Sealing body

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[Procedure amendment]

[Submission date] January 19, 2000 (2000.1.1)
9)

[Procedure amendment 1]

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[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Explanation of sign

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[Procedure amendment 3]

[Document name to be amended] Drawing

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Claims (7)

[Claims] 1. A positive electrode of lithium ions by charge and discharge using the positive electrode active material doped with and dedoped, the non-aqueous secondary battery having a negative electrode and the separator, the above positive electrode active material, the general formula Li _x Mn _y O _{4 -z} , and for y and z in the above formula, 0.48 ≦ y / 4−z ≦ 0.52,0
<Z ≦ 0.15, and x is a spherical or elliptical spinel-type lithium manganese oxide that is restricted to a range of 0.10 ≦ x ≦ 0.95 in any state of charge and discharge; A non-aqueous secondary battery, wherein the open terminal voltage of the battery is 3 V or more. 2. The non-aqueous secondary battery according to claim 1, wherein the Fe content in the spinel-type lithium manganese oxide is 200 ppm or less. 3. The non-aqueous secondary battery according to claim 1, wherein the spinel-type lithium manganese oxide has an average particle size of 1 to 45 μm. 4. A non-aqueous secondary battery having a positive electrode, a negative electrode, and a separator using a positive electrode active material doped and dedoped with lithium ions by charging and discharging, wherein the positive electrode active material has a general formula Li _x (Mn _{1− b} A _b ) _y O _4-z , where y and z in the above formula are 0.48 ≦ y / 4-z
≦ 0.52, 0 <z ≦ 0.15, and A is Al, C
represents at least one of u, Fe, Ni, Co, Cr, B and Si, where 0 <b ≦ 0.1, and x is 0.10 ≦ x in any state of charge and discharge.
A non-aqueous secondary battery, which is a spherical or elliptical spinel-type lithium manganese oxide regulated to a range of ≦ 0.95 and has an open terminal voltage of 3 V or more. 5. A method of using a non-aqueous secondary battery having a positive electrode, a negative electrode, and a separator using a positive electrode active material doped and dedoped with lithium ions by charge and discharge, wherein the positive electrode active material has a general formula Li _x Mn represented by _y O _4-z ,
With respect to y and z in the above formula, 0.48 ≦ y / 4−z ≦
0.52, a spherical or elliptical spinel-type lithium manganese oxide in which 0 <z ≦ 0.15, wherein x is 0.1 in both the charge and discharge states.
A method for using a non-aqueous secondary battery, characterized in that the battery is used in a voltage range in which the open terminal voltage is 3 V or higher, and the battery is restricted to a range of 0 ≦ x ≦ 0.95. 6. A method of using a non-aqueous secondary battery having a positive electrode, a negative electrode, and a separator using a positive electrode active material doped and dedoped with lithium ions by charge and discharge, wherein the positive electrode active material is Li _x (Mn ₁ is represented by _{-b a b) y O 4-} z, y in the above formula, for z, 0.48 ≦ y / 4-
z ≦ 0.52, 0 <z ≦ 0.15, and A is Al, C
u, Fe, Ni, Co, Cr, B, or Si, a spherical or elliptical spinel-type lithium manganese oxide in which 0 <b ≦ 0.1, wherein x is charge and discharge 0.1 in any state of
A method for using a non-aqueous secondary battery, characterized in that the battery is used in a voltage range in which the open terminal voltage is 3 V or higher, and the battery is restricted to a range of 0 ≦ x ≦ 0.95. 7. The method for using a non-aqueous secondary battery according to claim 5, wherein the charging is constant current / constant voltage charging.