JPH11233112A - Preparation of lithium manganate compound for lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily exhibit all the properties such as a charge.discharge characteristic of high capacity in the cases where a lithium manganate compound is used as an positive electrode material for a lithium ion secondary battery. SOLUTION: This method comprises combination of a manganese oxyhydroxide preparing process where water is added to MnSo4 hydrate to be adjusted to 0.08-0.8 mol/l of aqueous solution, the resuting mixture is heated to 10-80 deg.C, hydrogen peroxide is dropped to it to be stirred vigorously, aqueous ammonia is added thereafter, the resulting mixture is still standed after stirred, and where a precipitate is washed after filtration to prepare manganese oxyhydroxide dried by 20-40 deg.C of air and pulverized (150 μm or less), and a lithium manganate preparing process where the manganese oxyhydroxide is mixed with lithium hydroxide at 30-60 of mixing ratio to conduct hydrothermal reaction at 140-300 deg.C, and where filtration-washing-drying under vacuum is carried out to prepare lithium manganate. A process for heat-treating the lithium manganate under atmosphere of 100-200 deg.C is preferably combined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lithium manganate compound used as a positive electrode material of a lithium ion secondary battery.

[0002]

2. Description of the Related Art Generally, manganese oxyhydroxide, that is, γ
A method for producing manganese oxyhydroxide is described in K. Matsuk
i, et. al. (Electrochemica Acta.31 (1986) 13)
Is known for. The production of lithium manganate from γ-type manganese oxyhydroxide and lithium hydroxide is known from Tabuchi's dissertation (Solid.stat.ionics, 89 (1996) 53). For lithium manganate compounds, the development of high-voltage, high-energy-density lithium-ion secondary batteries is being promoted by combining positive electrode materials for lithium-ion secondary batteries and negative electrode materials such as carbon materials capable of occluding and releasing lithium. ing. The lithium manganate compound of the positive electrode material for lithium ion secondary batteries is composed of a powder of LiOH · H ₂ O and γ-
A method is also known in which a powder made of MnOOH is fired at 450 ° C. in a nitrogen atmosphere to produce LiMnO ₂ . However, using these powders, high capacity LiMnO
_In order to obtain ₂ , LiOH · H ₂ O powder and γ-MnOOH
A homogeneous mixture of powders must be formed prior to firing.
Insufficient homogeneity of these mixtures prior to firing to obtain a uniformly lithiated material can result in the formation of undesirable compounds or unreacted materials remaining as impurities, The electrochemical activity of the material was reduced, and characteristics such as charge / discharge capacity were reduced. Therefore, development of compounds such as LiMnO ₂ particularly suitable for use as a cathode material of a lithium ion secondary battery has been actively conducted. For example, the method described in JP-A-8-241716 discloses a method of While simplifying the manufacturing process of the positive electrode active material using the reaction of hydroxides and oxyhydroxides with alkalis such as LiOH, the reaction efficiency of alkalizing the hydroxides and oxyhydroxides is increased,
A method has been proposed in which a positive electrode active material having a uniform composition and a high capacity can be obtained.

[0003]

However, lithium manganate compounds produced by any of the methods already proposed have high capacity charge-discharge characteristics when used as a positive electrode material for lithium ion secondary batteries. Nothing satisfies all of the properties, and further development is currently desired.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In view of the above, research was conducted to develop a method for producing a lithium manganate compound particularly suitable for use as a cathode material for a lithium ion secondary battery. As a result, manganese oxyhydroxide used as a raw material was γ-type. Even if manganese oxyhydroxide other than manganese oxyhydroxide is mixed, if it is manufactured by combining the synthesis under hydrothermal conditions and the process of adjusting the amount of oxygen by heat treatment in the atmosphere, it is necessary to produce a powder that can demonstrate practically sufficient performance. I learned that I can do it.

The present invention has been made on the basis of the above-mentioned findings, and a method for producing a lithium manganate compound for a lithium ion secondary battery according to the present invention comprises adding MnSO ₄ hydrate to water by adding 0.08 wt. After adjusting to an aqueous solution of ~ 0.8 mol / l, heating to 10 ~ 80 ° C, adding hydrogen peroxide dropwise, stirring vigorously, adding aqueous ammonia, further stirring, leaving still, filtering and washing the precipitate And a step of producing manganese oxyhydroxide of 20-40 ° C. hot air drying-pulverization (150 μm or less) and mixing the manganese oxyhydroxide and lithium hydroxide at a mixing ratio of 30-60 to 140-300 A lithium manganate compound for a lithium ion secondary battery, comprising a combination and combination of steps of producing a lithium manganate that is reacted under hydrothermal conditions at a temperature of 400 ° C., and dried under a reduced pressure of filtration-washing-reduction. Manufacture Is the law.

In order to obtain higher battery characteristics,
Add water to MnSO ₄ hydrate and add 0.08 to 0.8 mol
/ 1 aqueous solution, heated to 10 to 80 ° C, added dropwise with hydrogen peroxide, stirred vigorously, added aqueous ammonia, further stirred and allowed to stand, filtered, washed the precipitate, ~ 4
Hot air drying at 0 ° C.—a process for producing crushed (150 μm or less) manganese oxyhydroxide and a mixing ratio of manganese oxyhydroxide and lithium hydroxide of 30 to 60 and 140 to
The reaction is carried out under hydrothermal conditions of 300 ° C., and a step of producing lithium manganate which is filtered, washed and dried under reduced pressure.
A method for producing a lithium manganate compound for a lithium ion secondary battery, comprising a combination of steps of performing a heat treatment in an atmosphere at a temperature of ° C.

Next, in the method for producing a lithium manganate compound for a lithium ion secondary battery according to the present invention, in order to produce a lithium manganate compound for obtaining excellent battery characteristics, that is, a charge / discharge capacity, first, sulfuric acid is used. Γ-MnO (OH) produced by adding aqueous hydrogen peroxide and aqueous ammonia to an aqueous solution of manganese () is obtained by dehydration. Its γ-Mn
In order to react OOH and lithium hydroxide to form a lithium manganate compound, the production conditions in each step were limited as follows, and the reason will be described below.

(A) Production step of MnOOH Adjustment is made by adding H ₂ O to MnSO ₄ hydrate.
If the amount is less than 0.8 mol / l, the yield is unfavorably decreased. On the other hand, if the amount exceeds 0.8 mol / l, a heterogeneous precipitate is formed to hinder the reaction. 0.8 mol / l.

If the heating temperature of MnSO ₄ hydrate is less than 10 ° C., the synthesis reaction is not accelerated, which is not preferable.
If the heating temperature exceeds 10 ° C., the reaction is accelerated, but the insertion of additives such as hydrogen peroxide may be dangerous.
It was determined to be 80 ° C. Preferably, it was set to 30 to 60 ° C.

If the hot air drying temperature of MnOOH is less than 20 ° C., drying cannot be sufficiently performed, and if it exceeds 40 ° C., the MnOOH structure starts to collapse.
It was determined to be 0 ° C.

(B) Production process of lithium manganate The allowable range of the mixing ratio of MnOOH and LiOH.H ₂ O is 3
If it is less than 0, conversion to LiMnO ₂ does not occur.
If it exceeds 0, the effect of producing LiMnO ₂ is not improved and does not change. Therefore, the mixing ratio is set to 30 to 60.

If the reaction temperature of MnOOH and LiOH.H ₂ O under hydrothermal conditions is lower than 140 ° C., the reaction does not proceed. On the other hand, if it exceeds 300 ° C., a critical state is reached, so that operation becomes impossible. The reaction temperature was determined to be 0-300C.

[0013] (c) heat treatment step LiMnO ₂ annealing heat treatment temperature but is performed as required by the lithium manganate becomes difficult oxygen-amount adjustment is less than 100 ° C., whereas, of LiMnO ₂ exceeds 200 ° C. Because the structure starts to collapse. The heat treatment temperature range is 100
２００200 ° C.

[0014]

Next, the method for producing a lithium manganate compound for a lithium ion secondary battery according to the present invention will be described in detail with reference to examples. Using an ordinary chemical reaction apparatus, each step of the production methods 1 to 8 of the present invention and the comparative production methods 1 to 7 was adjusted according to the processing conditions shown in Table 1, and the production method of the present invention
In the production process of MnOOH of ~ 8, the aqueous solution concentration (mol / l) of manganese sulfate pentahydrate was changed from 0.01 to 0.8 mol / l, and the volume (l) of the aqueous solution of manganese sulfate pentahydrate was Constant 1 (same for the comparative production method) and solution temperature (° C) of 10
８０80 ° C., then hydrogen peroxide (ml) was 4-25
0 ml, and diluted ammonia water (l) 0.1 ~
The amount was 8 liters, the dilution amount (times) of the ammonia water at that time was a constant 80 times (the comparative production method was the same), and the precipitation washing water amount (l) was 0.3 to 60 liters. On the other hand, at least one of the comparative production methods 1 to 7 is out of the range of each of the above conditions. Next, in the production steps of lithium manganate of production methods 1 to 8 of the present invention, the mixing ratio of MnOOH and LiOH.H ₂ O was set to 30 to 60, and the purity (%) of LiOH-hydrate was 9%.
9% (same for comparative manufacturing method)
The temperature (° C.) varied from 140 to 300 ° C., the time (hr) varied from 2 to 30 hours, and the pH after washing was kept constant at 9 (the same applies to the comparative production method). On the other hand, at least one of the comparative production methods 1 to 7 is out of the respective ranges described above. Furthermore, in the heat treatment step of lithium manganate of the production methods 1 to 8 of the present invention, the atmosphere of the heat treatment conditions was nitrogen or oxygen, and the heat treatment temperature range was 100 to 200 ° C. On the other hand, comparative production methods 1 to 7
The heat treatment atmosphere was oxygen, nitrogen or none.

Using the lithium manganate compound of the present invention as the positive electrode of a lithium ion secondary battery, the initial charge capacity (Ah / kg) and the charge capacity after 20 cycles (Ah / kg) are measured using a normal charge / discharge tester. The lithium manganate compound product was measured and evaluated, and the results are shown in Table 1.

[0016]

[Table 1]

[0017]

As can be seen from the results shown in Table 1, the lithium manganate compounds of the methods 1 to 8 of the present invention for producing lithium manganese compounds for lithium ion secondary batteries were used as the positive electrode material of lithium ion secondary batteries. While the storage batteries have high capacity, and show a favorable result that the capacity decrease when the charge / discharge cycle is repeated is remarkably small compared to a storage battery using a conventional lithium manganate compound as a positive electrode material, As is apparent from the storage batteries using the lithium manganate compounds of Comparative Production Methods 1 to 7 as positive electrode materials, it is apparent that the storage batteries do not exhibit sufficiently satisfactory performance in terms of charge / discharge capacity. As described above, especially when the lithium manganate compound of the present invention is used as a positive electrode material of a lithium ion secondary battery, a large charge / discharge capacity can be ensured over a long cycle life of the storage battery. It has industrially useful characteristics such as contributing to cost reduction.

Claims (2)

[Claims] In a method for producing a lithium manganate compound for a lithium ion secondary battery, water is added to MnSO ₄ hydrate to adjust to an aqueous solution of 0.08 to 0.8 mol / l, , Heated with hydrogen peroxide, stirred vigorously, added with ammonia water, further stirred, allowed to stand, filtered, washed the precipitate, dried with warm air at 20-40 ° C-crushed
(150 micron or less) manganese oxyhydroxide manufacturing process and a mixing ratio of manganese oxyhydroxide and lithium hydroxide of 3
A lithium ion mixture comprising a combination of steps of producing lithium manganate which is mixed at 0 to 60, reacted under a hydrothermal condition of 140 to 300 ° C., and dried under filtration, washing, and reduced pressure. For producing lithium manganate compounds for secondary batteries. 2. A method for producing a lithium manganate compound for a lithium ion secondary battery, wherein water is added to MnSO ₄ hydrate to adjust to an aqueous solution of 0.08 to 0.8 mol / l, , Heated with hydrogen peroxide, stirred vigorously, added with ammonia water, further stirred, allowed to stand, filtered, washed the precipitate, dried with warm air at 20-40 ° C-crushed
(150 microns or less) Manufacture of manganese oxyhydroxide and a mixture of manganese oxyhydroxide and lithium hydroxide at a mixing ratio of 30 to 60, and react under hydrothermal conditions of 140 to 300 ° C., filtration and washing A lithium ion secondary battery comprising a combination of a step of producing lithium manganate which is dried under reduced pressure and, if necessary, a step of heat-treating lithium manganate in an atmosphere at 100 to 200 ° C. For producing lithium manganate compounds.