JPH10116615A - Production of positive electrode material and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase charge and discharge capacity, enhance charge and discharge cycle characteristics, and lengthen a life of a nonaqueous electrolyte secondary battery using lithium manganese oxide as positive electrode material. SOLUTION: A transition metal compound is sedimented in lithium manganese oxide (Lix MOy ) in which diffraction peak intensity ratios of a diffraction plane (400) and a diffraction plane (311) by X-ray diffraction are in a range of 1.05<=(400)/(311)<=1.20, more preferably 1.10<=(400)/(311)<=1.15. Simultaneously, the lithium manganese oxide containing the sedimented transition metal compound is dried and dehydrated in vacuum at a temperature of 150 deg.C or less so as to produce positive electrode material. The lithium manganese oxide uses one among LiMn2 O4 , Li1+x Mn2 O4 , Li2 MnO3 , LiMnO2 , Li2 MnO3 , and the additional element of the transition metal uses one among Ni, Co, Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery which has excellent charge / discharge cycle characteristics and can be used stably for a long period of time.

[0002]

2. Description of the Related Art In recent years, portable telephones, headphone stereos,
The development of small electronic devices such as notebook computers has been remarkable, and there has been an increasing demand for small and large-capacity power supplies used for them. Conventionally, lead batteries, NiCd batteries, NiMH batteries having a larger capacity, and lithium ion secondary batteries have been put to practical use for these electronic devices. This lithium ion secondary battery has L
A secondary battery using iCoO ₂ or LiNiO ₂ , a lithium-doped and undoped carbon material for the negative electrode, and a non-aqueous electrolyte as an electrolyte. The spread has been remarkable.

[0003] In addition, research and development of lithium manganese oxide as a battery material has been actively carried out, and various synthetic methods and composite oxides using added metals have been studied. However, there has been no detailed report on the treatment of these materials so far, and mainly reports have been made on the composition ratio of the amount of lithium and the amount of oxygen.

On the other hand, the theoretical capacity of lithium manganese oxide is 148 mAh per unit mass in LiMn ₂ O _4.
/ G, and thus how to increase the available capacity was a technical goal. For this purpose, for example, a lithium manganese oxide powder crystal may have a function of smoothly promoting the insertion / desorption reaction of ions, and the like.However, in a conventionally proposed method of synthesizing a powder crystal,
The initial capacity in charge and discharge is about 110 mAh / g,
The capacity after the 00 cycle was less than 80% of the initial capacity.

[0005] As described above, the performance of lithium manganese oxide cannot be greatly improved only by specifying the composition ratios of the lithium amount and the oxygen amount, but only a slight improvement in the capacity and an improvement in the cycle characteristics. It is. Therefore, it is difficult to produce a practical battery using this material, and it has not been possible to mass-produce the battery industrially.

On the other hand, it is difficult to form a LiMn ₂ O ₄ powder material into a sheet electrode having a large capacity and flexibility, and it is difficult to prepare a practical electrode. In addition, even when a battery is formed using this material, it is recognized that the charge / discharge performance rapidly decreases as lithium enters and exits. Could not be used for development.

Further, as disclosed in Japanese Patent Application Laid-Open Nos. 6-111819 and 7-282798, as the charge / discharge cycle is performed, the oxidation number of manganese becomes non-uniform at high potentials. It is stated that a dissolution phenomenon occurs. In order to prevent LiMn ₂ O _{4 from} deteriorating its performance in charge and discharge cycles and to secure long-term stability, various materials and manufacturing methods have been studied, but sufficient problems have yet to be solved. There is no present.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to increase the charge / discharge capacity, improve the charge / discharge cycle characteristics, and extend the life of a nonaqueous electrolyte secondary battery using lithium manganese oxide as a cathode material. Accordingly, a battery suitable as a power source for a portable electronic device is provided.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above-mentioned problems.
00) and lithium manganese oxide intensity ratio of the diffraction peak is within a predetermined range of the diffraction plane (311) (Li _X MnO
_y ), a transition metal compound is precipitated, and the lithium manganese oxide containing the precipitated transition metal compound is dried and dehydrated in a vacuum at a temperature of 150 ° C. or lower to produce a positive electrode material. .

The intensity ratio of the diffraction peak by the X-ray diffraction is 1.05 ≦ [diffraction intensity of the diffraction surface (400)] /
[Diffraction intensity of diffraction surface (311)] ≦ 1.20, more preferably 1.10 ≦ [Diffraction intensity of diffraction surface (400)] /
Use of a lithium manganese oxide satisfying [diffraction intensity of diffraction surface (311)] ≦ 1.15.

Further, the lithium manganese oxide is Li
Mn ₂ O ₄ , Li _{1 + x} Mn ₂ O ₄ , LiMn ₂ O ₃ , L
Using one of the substances selected from the group consisting of iMnO ₂ and Li ₂ MnO ₃ .

Further, the additive element of the transition metal is Ni,
Co, one of the elements selected from the group of Fe, wherein the precipitated Co, Ni, Fe is 0.005 ≦ Me / Mn
≦ 0.02.

Further, in a non-aqueous electrolyte secondary battery using a lithium manganese oxide as a positive electrode material and a lithium metal, a lithium alloy, or a carbon material capable of being doped and dedoped with lithium as a negative electrode material, A non-aqueous electrolyte secondary battery is configured using the positive electrode material obtained by the method, and the above-described problem is solved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a conventional method for producing lithium manganese oxide, a method of mixing raw material powders and appropriately controlling the temperature, a method of controlling the heat treatment temperature in multiple stages, and a method of mixing lithium and manganese have been proposed. There are a method of controlling the ratio, a method of controlling by a long-time temperature treatment, and the like. In the present embodiment, a two-stage manufacturing method of controlling the mixture ratio of lithium and manganese, mixing and heat-treating the mixture is used. .

For the treatment of lithium and manganese oxides with Co and Ni, sulfuric acid compounds, nitric acid compounds, chlorides, oxalic acid compounds, halogen compounds, acetic acid compounds, cyanide compounds, hexaammine compounds, ethylenediamine compounds, pentanedionate compounds, A dilute solution such as a thiocyan compound can be used. These treatments can be performed by a precipitation treatment in a general aqueous solution.

The processing conditions are such that the solid component ratio in the solution is about 10%, and the hydrogen ion concentration in the solution is PH9 as the end point. The change in the hydrogen ion concentration is made to occur gradually in order to obtain a uniform processing effect. As the aqueous solution used for the precipitation treatment, aqueous ammonia, an aqueous alkali solution, amines and the like can be used, and a dilute alkali solution such as an aqueous LiOH solution is particularly preferable. Any means may be used for taking out the powder after the precipitation treatment as long as it can be filtered and washed.

The method for producing a lithium manganese oxide First, lithium hydroxide and manganese oxyhydroxide Li:
Mix at an atomic ratio of Mn = 0.515: 1. Next,
This mixture is placed in an alumina crucible and heat-treated at 350 ° C. for 2 hours in an oxygen atmosphere in an electric furnace. This is once taken out, mixed again in a mortar, put again in an alumina crucible, and heat-treated at 700 ° C. for 16 hours in an oxygen atmosphere in an electric furnace. Then, it cools to room temperature and grinds. When the material powder obtained by the above-described method was measured by an X-ray diffraction method, it coincided with the peak of spinel type LiMn ₂ O ₄ . Further, the diffraction intensity ratio between the diffraction plane (311) and the diffraction plane (400) of the crystal lattice of this material was 1: 1.12.

Example 1 Ni treatment is performed on LiMn ₂ O ₄ obtained as described above using an Ni compound in an aqueous solution. First, nickel chloride is dissolved in water to a concentration of 0.005 mol / liter to prepare a 500 ml nickel aqueous solution.
23 g of LiMn ₂ O ₄ was dissolved in this nickel aqueous solution,
The pH of the solution is adjusted to 9.0 by gradually adding a 5% aqueous solution of LiOH while stirring. In this state, the mixture is stirred for 1 hour, then filtered using a glass filter, and washed with pure water to extract a solid component. Next, the solid component was dried in a vacuum dryer at a temperature of 130 ° C. under a pressure of 10 ⁻² mmHg for 1 hour.
Dry for 2 hours to remove residual hydroxyl groups. As a result of measuring the material powder thus obtained by X-ray analysis, it was found that the diffraction peak was only of spinel type LiMn ₂ O ₄ . The diffraction plane (311) and the diffraction plane (40)
The diffraction intensity ratio of 0) was also the same.

Example 2 Ni treatment is performed on LiMn ₂ O ₄ obtained as described above using a Ni compound in an aqueous solution. Nickel chloride is dissolved in water so as to have a concentration of 0.0025 mol / liter to prepare a 500 ml aqueous nickel solution, and Ni treatment of LiMn ₂ O ₄ is performed in this solution in the same manner as in Example 1. The obtained solid component was heated at 150 ° C.
Dry under a pressure of 0 ^-2 mmHg for 12 hours to remove residual hydroxyl groups. As a result of measuring the material powder obtained in this manner by X-ray analysis, spinel-type LiMn ₂ O
Only ₄ diffraction peaks were obtained. Further, the diffraction intensity ratio between the diffraction surface (311) and the diffraction surface (400) of this material was also the same.

EXAMPLE 3 Ni treatment is performed on LiMn ₂ O ₄ obtained as described above using a Ni compound in an aqueous solution. Nickel chloride is dissolved in water so as to have a concentration of 0.01 mol / liter to prepare a 500 ml aqueous nickel solution, in which Ni treatment of LiMn ₂ O ₄ is performed in the same manner as in Example 1. The obtained solid component was heated in a vacuum dryer at a temperature of 120 ° C. and 10 ⁻² m.
It is dried under a pressure of mHg for 12 hours to remove the remaining hydroxyl groups. As a result of measuring the material powder thus obtained by X-ray analysis, it was found that the diffraction peak was only of spinel type LiMn ₂ O ₄ . In addition, the diffraction surface of this material (31
The diffraction intensity ratio between 1) and the diffraction surface (400) was also the same.

Comparative Example 1 Ni treatment of LiMn ₂ O ₄ is performed under the same conditions as in Example 1. The obtained solid component was heated at a temperature of 300 ° C.
Dry under a pressure of 0 ^-2 mmHg for 12 hours to remove residual hydroxyl groups. As a result of measuring the material powder obtained in this manner by X-ray analysis, spinel-type LiMn ₂ O
Only ₄ diffraction peaks were obtained. The diffraction intensity ratio between the diffraction surface (311) and the diffraction surface (400) of this material is: diffraction intensity of the diffraction surface (311): diffraction intensity of the diffraction surface (400) =
1: 1.13.

Comparative Example 2 Ni treatment of LiMn ₂ O ₄ is performed under the same conditions as in Example 1. The obtained solid component was heated at a temperature of 13 using a gear oven.
Dry at 0 ° C. for 12 hours to remove residual hydroxyl groups. As a result of measuring the material powder thus obtained by X-ray analysis, it was found that the diffraction peak was only of spinel type LiMn ₂ O ₄ . The diffraction intensity ratio between the diffraction surface (311) and the diffraction surface (400) of this material was: diffraction intensity of the diffraction surface (311): diffraction intensity of the diffraction surface (400) = 1: 1.12.

Comparative Example 3 Ni treatment of LiMn ₂ O ₄ is performed under the same conditions as in Example 1. The obtained solid component was heated at a temperature of 30 using a gear oven.
Dry at 0 ° C. for 12 hours to remove residual hydroxyl groups. As a result of measuring the material powder thus obtained by X-ray analysis, it was found that the diffraction peak was only of spinel type LiMn ₂ O ₄ . The diffraction intensity ratio between the diffraction surface (311) and the diffraction surface (400) of this material was: diffraction intensity of the diffraction surface (311): diffraction intensity of the diffraction surface (400) = 1: 1.13.

Preparation of Test Battery A coin-type battery was prepared using the seven types of materials obtained as described above as positive electrode materials.

As shown in FIG. 1, a coin-type battery 1 has a thickness of 1.6 mm and a diameter of 17 mm as a negative electrode material 3 in a battery can 2.
Then, a lithium gasket 4 made of polypropylene for insulation is arranged along the side wall of the battery can 2. On the other hand, 90% by weight of the positive electrode material, 7% by weight of graphite, and 3% by weight of polyvinylidene fluoride as a binder were mixed.
With a press machine with aluminum net 15m in diameter
m to form a positive electrode pellet 5. The positive electrode pellet 5 is placed on the terminal cover 6, and a polypropylene separator 7 is further placed thereon. Propylene carbonate and dimethyl carbonate were mixed at a ratio of 1: 1 as an electrolytic solution, and a solution in which LiPF ₆ was dissolved at a ratio of 1 mol / liter was poured into the terminal cover 6. And sealed by caulking to produce a battery.

Battery test LiMn ₂ O ₄ without Ni treatment, LiM of Examples 1-3
n ₂ O ₄ , and LiMn ₂ O ₄ of Comparative Examples 1 to 3 were used as positive electrode materials, and a plurality of batteries were produced by the above-described method.
These batteries were subjected to a discharge load performance test and a charge / discharge cycle test under the following conditions.

First, the battery was charged at a current density of 0.5 mA / cm ² and an upper limit voltage of 4.2 V for 12 hours.
Discharge to 3.0 V at A / cm ² , then 1.0 mA
/ Cm ² , after charging for 5.5 hours at an upper limit voltage of 4.2 V,
A cycle of discharging to 3.0 V at a current density of 1.0 mA / cm ² is repeated five times. Thereafter, these batteries are divided into a discharge load performance test, a charge / discharge cycle test, and a capacity test before and after storage, and subjected to tests.

The discharge load performance test was conducted at a current density of 1.0 mA /
After charging for 5.5 hours at cm ² and upper limit voltage of 4.2V,
A test was performed three times each for discharging to 3.0 V at a predetermined value within a current density range of 0.5 to 5.0 mA / cm ² , and the capacity (mAh / g) at that time was measured. The result is shown in FIG.

In the charge / discharge cycle test, the current density was 1.
After charging for 5.5 hours at 0 mA / cm ² and an upper limit voltage of 4.2 V, a cycle test of discharging to 3.0 V at a current density of 1.0 mA / cm ² was repeated, and the capacity at that time (m
Ah / g) was measured at each predetermined cycle. The result is shown in FIG.

As shown in FIG. 2, as a result of the discharge load performance test, LiMn ₂ O ₄ was subjected to Ni treatment at all current densities and dried in a vacuum at a temperature of 150 ° C. or less.
3 shows that excellent capacity is maintained.

FIG. 3 shows that Examples 1 to 3 show excellent cycle characteristics. This is because moisture adsorbed on the surface of the powder can be dried sufficiently at normal pressure, but when the transition metal compound is dehydrated and dried at several hundred degrees Celsius, not only dehydration but also the precipitated transition metal compound is dehydrated after the dehydration reaction. , Cause partial crystallization and regular arrangement, and enter the inside of LiMn ₂ O ₄ , which is considered to cause a decrease in cycle characteristics.
Therefore, it is considered that Examples 1 to 3 dried in vacuum show good characteristics. This is thought to be due to the fact that when the properties of the transition metals are similar, the phenomena of mutual substitution and diffusion occur, but the same also occurs in metal compounds and the like.

The fact that the effect of the hydroxide remaining under vacuum drying conditions at a relatively low temperature as described above is small is as follows.
It can be confirmed from the fact that the capacity decreases in Examples 1 to 3 are slight. However, the precipitated transition metal is M
When e / Mn = 0.02 or more, the oxide starts to show the properties of the resistor layer after the heat treatment, and as the cycle progresses,
This gradually causes a decrease in capacity.

Further, the other batteries thus produced were subjected to a current density of 1.
After charging at 0 mA / cm ² and an upper limit voltage of 4.2 V for 5.5 hours, discharging at a current density of 1.0 mA / cm ² to 3.0 V, measuring the capacity before storage, and stopping at the next charging state. These charged batteries were stored at a temperature of 60 ° C. for 10 days, and the stored batteries were stored at a current density of 1.0 mA / cm ² .
The battery was discharged to 0 V, the capacity after storage was measured, and the battery was then charged with a current density of 1.0 mA / cm ² and an upper limit voltage of 4.2 V.
After charging for 5.5 hours at a current density of 1.0 mA / cm ²
, A charge / discharge test for discharging to 3.0 V was performed twice, and the recovery capacity after storage was measured. Table 1 shows the results.

[0034]

[Table 1]

As shown in Table 1, it is understood that the batteries of Examples 1 to 3 have excellent recovery capacities after storage and after storage. From the above test results, it is found that a battery using a material obtained by subjecting LiMn ₂ O ₄ to Ni treatment and vacuum-drying at a temperature of 150 ° C. or less exhibits excellent discharge load characteristics, charge / discharge cycle characteristics, and capacity retention performance.

Further, according to the method of the present invention,
Unlike the powdered material obtained by combining other materials described in JP-A-111819, the capacity is not impaired, the discharge load characteristics, the charge / discharge cycle characteristics, and the stability at high temperatures are obtained. A battery having excellent performance can be formed, and a more stable manufacturing method can be obtained.

When the battery after the charge / discharge cycle was disassembled, no discoloration due to manganese elution or manganese precipitation at the negative electrode was observed in any of the materials subjected to the transition metal treatment. It has been confirmed that there is an effect described in JP-A-7-282798 to suppress the precipitation of manganese in the electrolytic solution.

Further, according to the method of the present invention, the results of X-ray diffraction of LiMn ₂ O ₄ before Ni treatment shown in FIG.
From the X-ray diffraction results of Example 1 in which n ₂ O ₄ was treated with Ni and dried at a temperature of 130 ° C., the diffraction surface (311) and the diffraction surface (4
It can be seen that water and hydroxyl groups can be removed without changing the ratio of the X-ray diffraction peak intensities of (00).

In this embodiment, the positive electrode material according to the present invention is used for a coin-type non-aqueous electrolyte secondary battery. However, the present invention is not limited to this, and the present invention is not limited to this. It may be used for any type of battery, such as an inside-out type cylindrical battery, and may be used for any size battery.

Also, the case where LiMn ₂ O ₄ is used as the cathode material has been described, but Li _{1 + x} Mn ₂ O ₄ , L
Any of iMn ₂ O ₃ , LiMnO ₂ , and Li ₂ MnO ₃ may be used.

[0041]

As is clear from the above description, the use of the lithium manganese oxide of the present invention increases the charge / discharge capacity, improves the charge / discharge cycle performance, and further improves the current dependency after the cycle has elapsed. A certain decrease in discharge load performance is reduced, and the device can be used stably for a long period of time.

In addition, it was confirmed that, regardless of the conductive material and the particle size, the charge / discharge reactivity and the ionic conductivity were maintained efficiently in any mixed state, and the conventional LiCoO ₂ or LiNiO _{2 A} secondary battery having the same performance as a lithium ion secondary battery using ₂ as a positive electrode and a carbon material as a negative electrode can be configured.

Further, in the conventional lithium manganese oxide, when the charge / discharge cycle is performed for a long time, the capacity is reduced and the discoloration of the separator is often caused. In the lithium manganese oxide of the present invention, the oxidation number of manganese in this material is increased. Can prevent the dissolution of lithium and, therefore, the discoloration of the separator.

By performing dehydration and drying by the above-described method, a lithium manganese oxide material that does not cause lithium ion inactivation at a low temperature can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a coin-type battery using a positive electrode material according to the present invention.

FIG. 2 is a diagram showing a result of a discharge load performance test of a coin-type battery using a positive electrode material according to the present invention.

FIG. 3 is a view showing a result of a cycle characteristic test of a coin-type battery using a positive electrode material according to the present invention.

FIG. 4 is an X-ray diffraction result before LiMn ₂ O ₄ treatment.

FIG. 5: NiMn treatment of LiMn ₂ O ₄ , temperature of 130
It is the X-ray-diffraction result of Example 1 dried in vacuum at ° C.

[Explanation of Signs] 1 ... Coin type battery, 2 ... Battery can, 3 ... Negative electrode material, 4 ... Gasket, 5 ... Positive electrode pellet, 6 ... Terminal cover, 7 ... Separator

Claims (7)

[Claims] 1. A diffraction surface (400) of a powder by X-ray diffraction.
And a lithium manganese oxide (Li _x MnO _y ) in which the intensity ratio of the diffraction peak of the diffraction plane (311) is within a predetermined range.
In addition to precipitating the transition metal compound, the lithium manganese oxide containing the precipitated transition metal compound is dried in a vacuum at a temperature of 150 ° C. or less, and subjected to a dehydration treatment to produce a positive electrode material. Production method. 2. A lithium manganese alloy wherein the intensity ratio of the diffraction peak by the X-ray diffraction is 1.05 ≦ [diffraction intensity of diffraction surface (400)] / [diffraction intensity of diffraction surface (311)] ≦ 1.20. The method for producing a positive electrode material according to claim 1, wherein an oxide is used. 3. A lithium manganese having an X-ray diffraction diffraction peak intensity ratio of 1.10 ≦ [diffraction surface (400) diffraction intensity] / [diffraction surface (311) diffraction intensity] ≦ 1.15. The method for producing a positive electrode material according to claim 1, wherein an oxide is used. 4. The lithium manganese oxide is LiMn.
₂ O ₄ , Li _{1 + x} Mn ₂ O ₄ , LiMn ₂ O ₃ , LiM
One of the substances selected from the group consisting of nO ₂ and Li ₂ MnO ₃
The method for producing a positive electrode material according to claim 1, wherein: 5. The additive element of the transition metal is Ni, C
The method for producing a positive electrode material according to claim 1, wherein the element is one of elements selected from the group consisting of o and Fe. 6. The deposited Co, Ni, Fe comprises:
The method for producing a positive electrode material according to claim 5, wherein 0.005≤Me / Mn≤0.02. 7. A non-aqueous electrolyte secondary battery using a lithium manganese oxide as a positive electrode material and a lithium metal, a lithium alloy, or a carbon material capable of being doped and dedoped with lithium as a negative electrode material. A non-aqueous electrolyte secondary battery comprising a positive electrode material obtained by the manufacturing method according to claim 6.