JP2565259B2 - Organic electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electrolyte battery using manganese dioxide as a positive electrode active material, lithium or a lithium alloy as a negative electrode active material, and an organic electrolyte solution as an electrolytic solution. And particularly relates to improvement of the positive electrode active material.

SUMMARY OF THE INVENTION The present invention is an organic electrolyte battery comprising a positive electrode active material mainly composed of manganese dioxide, a negative electrode active material mainly composed of lithium or a lithium alloy, and an organic electrolytic solution, wherein the positive electrode active material has a large specific surface area. By using chemically synthesized manganese dioxide and controlling the weight ratio of the negative electrode active material to the positive electrode active material, it is intended to provide an organic electrolyte battery having excellent heavy load characteristics and a large discharge capacity.

[Conventional technology]

A so-called organic electrolyte battery that uses a light alloy such as lithium or a lithium alloy as a negative electrode active material and an organic electrolyte solution as an electrolyte solution has high energy density, low self-discharge, good leakage resistance, etc. It has various excellent features and is widely used as a memory backup power source for various small electronic devices such as calculators and watches.

By the way, in the field of this type of organic electrolyte battery, a battery using MnO ₂ , CF _x , FeS ₂ , CuO, CuFeS ₂ or the like as a positive electrode active material is generally put into practical use. Among them, the lithium manganese battery using manganese dioxide (MnO ₂ ) is an excellent battery system because of its high voltage, flat discharge voltage, and low material cost. Conventionally, an organic electrolyte battery using electrolytic manganese dioxide as a positive electrode active material has been put to practical use.

[Problems to be solved by the invention]

However, since the organic electrolyte solution has a low conductivity and a high liquid resistance as compared with the aqueous electrolyte solution, the application of the organic electrolyte battery is generally limited to those that perform light load discharge, and compared with the radio etc. It was unsuitable for applications that require static heavy load discharge (several mA discharge). For example, when receiving an FM broadcast on a card radio, it is required to discharge at about 5 to 7 mA, and it is the current situation that the conventional organic electrolyte battery using electrolytic manganese dioxide cannot be used.

Therefore, the present invention has been proposed in view of the above circumstances, and an object thereof is to provide an organic electrolyte battery having excellent heavy load characteristics and a large discharge capacity.

[Means for solving problems]

As measures against heavy loads in organic electrolyte batteries, attempts have been made to increase the facing area between the positive electrode and the negative electrode, study the relationship between the electrolyte composition and salt concentration, study the composition of the positive electrode active material, etc. As a result of earnest studies by the present inventors,
It has been found that the electrode reaction at the interface between the electrolytic solution and the positive electrode active material has a great influence on the heavy load characteristics.

The present invention focuses on the fact that particles having a large specific surface area can be obtained even with a practical particle size, and by using chemically synthesized manganese dioxide having a large specific surface area as the positive electrode active material, the interface between the electrolytic solution and the positive electrode active material is It is possible to increase the electrochemical reaction area, make it possible to smoothly carry out a battery reaction, and improve the active material utilization rate during heavy load discharge.

The organic electrolyte battery of the present invention has been completed based on such findings, and is an organic electrolyte comprising a positive electrode active material mainly containing manganese dioxide, a negative electrode active material mainly containing lithium or a lithium alloy, and an organic electrolyte solution. In the battery, the positive electrode active material manganese dioxide has a specific surface area of 50
Chemically synthesized manganese dioxide of about 90 m ² / g, characterized in that the weight ratio of the negative electrode active material to the positive electrode active material is 0.030 to 0.054.

In the present invention, as the chemically synthesized manganese dioxide used as the positive electrode active material, any of those chemically synthesized by a known synthesis method can be used. For example, manganese sulfate is used as a starting material, and manganese carbonate is used as the manganese carbonate. reaction,
It is possible to use those obtained by synthesizing a lower manganese oxide through an oxidation reaction or the like, and then making it heavy by a chlorate reaction. The obtained chemically synthesized manganese dioxide is extremely porous as compared with electrolytic manganese dioxide, and therefore has a very large specific surface area even with a practical particle size. In addition, this chemically synthesized manganese dioxide is a material that is obtained at a very low cost, has excellent performance, and exhibits excellent characteristics in terms of manufacturing cost.

In the chemically synthesized manganese dioxide having such a large specific surface area, the contact area with the electrolytic solution is expanded, and the electrochemical reaction area of the interface between the electrolytic solution and the chemically synthesized manganese dioxide is increased to smoothly perform the electrode reaction. And the utilization rate of the active material is improved. Here, in the present invention, the specific surface area of the chemically synthesized manganese dioxide is 50 to 90 m ² / g. This is because when the specific surface area is smaller than 50 m ² / g, the contact area with the electrolytic solution is reduced and a good battery reaction does not proceed. Further, when the specific surface area is larger than 90 m ² / g, the filling rate of manganese dioxide that is substantially filled decreases and it becomes difficult to secure the capacity.

On the other hand, the negative electrode active material is lithium or a lithium alloy,
Li-Al is the main component, and lithium may be used alone as the negative electrode active material. Alternatively, an alloy obtained by adding one or more of lead, tin, bismuth, cadmium, copper, iron, etc. to lithium can be used as the negative electrode active material. It may be used as a substance. When an alloy of lithium and the other metal is used as the negative electrode active material, it is preferable to add the other metal to the extent that the original potential of lithium is not significantly changed.

Here, the weight ratio (Li / MnO ₂ ) of the positive electrode active material and the negative electrode active material used in the organic electrolyte secondary battery is 0.030 to 0.
Restrict to 054. By setting the weight ratio of the negative electrode active material to the positive electrode active material within this range, the discharge capacity increases.

As the electrolytic solution used for the organic electrolyte secondary battery, a non-aqueous organic electrolyte solution in which a lithium salt is used as an electrolyte and is dissolved in an organic solvent is used.

Here, examples of the organic solvent include esters, ethers, 3-substituted-2-oxazolidinones, and mixed solvents of two or more of these.

Examples of the esters include alkylene carbonate (ethylene carbonate, propylene carbonate, γ-butyl lactone, 2-methyl-γ-butyl lactone, etc.) and the like.

Examples of ethers include diethyl ether, cyclic ethers such as ethers having a 5-membered ring [tetrahydrofuran; substituted (alkyl, alkoxy) tetrahydrofuran such as 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2-ethyltetrahydrofuran, 2,2 '.
-Dimethyltetrahydrofuran, 2-methoxytetrahydrofuran, 2,5-dimethoxytetrahydrofuran, etc .; dioxolane, etc.], ether having a 6-membered ring [1,4-dioxane, pyran, dihydropyran, tetrahydropyran],
Dimethoxyethane and the like can be mentioned.

The 3-substituted-2-oxazolidinones include 3-alkyl-2-oxazolidinones (3-methyl-2-oxazolidinones, 3-ethyl-2-oxazolidinones), 3-
Cycloalkyl-2-oxazolidinones (3-cyclohexyl-2-oxazolidinones), 3-aralkyl-2
Examples include -oxazolidinone (3-benzyl-2-oxazolidinone and the like) and 3-aryl-2-oxazolidinone (3-phenyl-2-oxazolidinone and the like).

Among them, propylene carbonate, ether having a 5-membered ring (particularly tetrahydrofuran, 2-methyltetrahydrofuran, 2-ethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-methoxytetrahydrofuran), 3-methyl-2-oxazolidinone and the like are preferable.

As the electrolyte, lithium perchlorate, lithium borofluoride, lithium phosphorus fluoride, lithium chloroaluminate,
Lithium halide, lithium trifluoromethanesulfonate, etc. can be used, and lithium perchlorate, lithium borofluoride, etc. are preferable.

[Action]

Conventionally, electrolytic manganese dioxide has been used as a positive electrode active material for lithium-manganese batteries. This electrolytic manganese dioxide is obtained by mechanically pulverizing densely deposited manganese dioxide on the electrode during electrolysis, and its specific surface area is determined by the average particle size that has reached, so it is practical. It has a relatively small value for particles with different particle sizes.

On the other hand, chemically synthesized manganese dioxide synthesized by the chemical synthesis method, on the other hand, can be obtained in a porous particle state by selecting the synthesis conditions, so that the pore volume can be increased, It is possible to obtain particles having a large specific surface area even with a practical particle size.

Therefore, the specific surface area of the positive electrode active material is 50 to 90 m ² / g.
In the organic electrolyte battery using the chemically synthesized manganese dioxide and using lithium as the negative electrode active material, it is possible to increase the electrochemical reaction area at the interface between the electrolytic solution and the positive electrode active material, and smoothly perform the electrode reaction. Therefore, the active material utilization rate at the time of heavy load discharge is improved.

In addition, the chemically synthesized manganese dioxide used as the positive electrode active material is very inexpensive in terms of material cost and easily available, which is advantageous in manufacturing as well as cost reduction of the battery.

Further, when the weight ratio of the negative electrode active material to the positive electrode active material is set to 0.030 to 0.054, the discharge capacity increases.

〔Example〕

Hereinafter, specific examples of the organic electrolyte battery to which the present invention is applied will be described with reference to the drawings.

First, chemically synthesized manganese dioxide used as a positive electrode active material of the organic electrolyte battery according to the present invention was synthesized.

Synthesis Example 1 0.4 mol each of a 3 mol / l manganese sulfate aqueous solution and a 3 mol / l ammonium carbonate aqueous solution in water kept at 60 ° C.
Manganese carbonate was obtained by dropping simultaneously at a rate of 1 / hr. The obtained manganese carbonate was subjected to a hydroxylation reaction at 40 ° C. for 15 hours while blowing nitrogen gas in 1.2 mol / l sodium hydroxide aqueous solution 2.2 l, and then the blowing gas was changed to air to give 1.5
Oxidation reaction of time was performed. Then, the liquid temperature was changed to water held at 50 ° C., and chlorine gas was blown in together with air to carry out an additional oxidation reaction for 3 hours.

The reaction product was filtered, washed with water, transferred to a mixed solution 1 of 0.5 mol / l manganese nitrate and 0.5 mol / l nitric acid, 58 g of sodium chlorate was added, and the mixture was heated at 85 ° C. for 2 hours to lower-oxidize manganese. A manganese dioxide sample A was obtained by dissolving the substance and making it heavy by the chlorate reaction. All the above reactions were carried out under sufficient stirring.

Synthesis Example 2 The synthesis temperature of manganese carbonate was 25 ° C., and the mixed solution amount of 0.5 mol / l manganese nitrate and 0.5 mol / l nitric acid in the heavy step by dissolution of manganese lower oxide and chlorate reaction was 0.8 l. A manganese dioxide sample B was obtained in the same manner as in Synthesis Example 1 except that the amount of sodium chlorate added was 24 g.

Synthetic Example 3 A manganese dioxide sample C was obtained in the same manner as in Synthetic Example 2 except that the amount of sodium chlorate added in the step of making heavy by the chlorate reaction was 5 g.

Synthesis Example 4 Manganese dioxide sample D was obtained in the same manner as in Synthesis Example 3 except that the synthesis temperature of manganese carbonate was 15 ° C.

Synthesis Example 5 Manganese dioxide sample E was obtained in the same manner as in Synthesis Example 3 except that the synthesis temperature of manganese carbonate was 10 ° C.

Synthetic Example 6 Up to the additional oxidation reaction step with chlorine was carried out in the same manner as in Synthetic Example 5, the obtained reaction product was filtered and washed with water, and then heated at 80 ° C. for 2 hours in 3 mol / l nitric acid to lower-oxidize manganese. The substance was dissolved to obtain a manganese dioxide sample F.

Synthesis Example 7 A manganese dioxide sample G was obtained in the same manner as in Synthesis Example 6 except that the synthesis temperature of manganese carbonate was 5 ° C.

Synthesis Example 8 1 mol / l sodium carbonate aqueous solution kept at 25 ° C.
A manganese dioxide sample H was obtained in the same manner as in Synthesis Example 6 except that 0.4 l of a 1 mol / l manganese sulfate aqueous solution was dropped into 4 l at a rate of 0.1 / hr to obtain manganese carbonate.

In addition to the chemically-synthesized manganese dioxide samples A to H obtained by the above method, as the chemically-synthesized manganese dioxide samples, the international common manganese dioxide sample IC-22 (Sample I) and the international common manganese dioxide sample IC-8 (Sample J ) Prepared.
Further, as a comparative sample, an international common manganese dioxide sample IC-17 (designated as sample K), which is electrolytic manganese dioxide, was prepared.

Table 1 shows the measurement results of the average particle size, the manganese dioxide purity, and the specific surface area by the BET method of the prepared manganese dioxide sample A to manganese dioxide sample K.

The following examples were performed using the above samples.

Preliminary Experiment 1 First, in order to investigate the characteristics of Samples A to J as positive electrode active materials, sample batteries were prepared which were provided with a large excess of negative electrode active material and a large amount of electrolyte solution relative to the positive electrode electric capacity. still,
Each manganese dioxide sample was neutralized with a dilute aqueous solution of sodium carbonate, filtered, dried, and further heat-treated at 420 ° C. for 4 hours to be used as an experimental example.

A schematic sectional view of the sample battery is shown in FIG. That is, as shown in FIG. 1, the positive electrode can (2) made of nickel-plated stainless steel has a weight of 0.2 g and a diameter of 1.1 cm.
The positive electrode mixture (1) pressure-molded at a pressure of 5 ton / cm ² is installed in the disk shape. The positive electrode mixture (1) is
Chemically synthesized manganese dioxide 88.9 parts by weight, graphite 9.3
It is composed of 1.8 parts by weight of polytetrafluoroethylene. Then, in the same manner as the positive electrode canister (2), in the negative electrode canister (4) made of nickel-plated stainless steel,
Lithium metal (3) with a diameter of 1.25 cm and a thickness of 0.12 cm is pressure bonded. These positive electrode mixture (1) and metallic lithium (3)
Are superposed through a polypropylene separator (5), and the positive electrode canister (2) is caulked through a polypropylene gasket (6) whose surface is coated with asphalt, whereby the gasket (6) becomes a negative electrode. It is compressed with the can (4) to maintain the airtightness inside the battery. The electrolyte has penetrated into the separator (5),
As the electrolyte, 0.2 g of lithium perchlorate dissolved in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 1: 1 at a ratio of 1 mol / l was used.

Since this sample battery is designed so that the capacity of the positive electrode is significantly smaller than the capacity of the negative electrode, the results obtained by measuring the discharge characteristics of the battery show the characteristics of the positive electrode. Further, by injecting a sufficient amount of the electrolytic solution into the battery, the influence of the electrolytic solution involved in the electrode reaction can be ignored.

Sample batteries A to sample K having a diameter of 20 mm and a height of 2.5 mm were assembled by using samples A to K as the positive electrode active material of the sample battery having the above-described structure.

Next, using these sample batteries A to K, constant current discharge at a current density of 5 mA / cm ² was performed at 20 ° C. to a final voltage of 2 V, and the battery capacities were measured.

The obtained battery capacity was converted into the capacity per unit volume of the positive electrode, and plotted with respect to the specific surface area of each of the manganese dioxide samples A to K and shown in FIG. As is clear from FIG. ² , a high capacity can be obtained with a chemically synthesized product having a specific surface area of manganese dioxide of 50 m ² or more, but the packing density decreases with an increase in the specific surface area, and therefore 90 m to obtain a predetermined battery capacity. It is regulated to ² / g or less.

Based on the results of the above preliminary experiments, a battery was prepared using chemically synthesized manganese dioxide data F and data I as positive electrode active materials and electrolytic manganese dioxide data K as a comparative example. In addition,
Each manganese dioxide material was neutralized and heat-treated in the same manner as in the case of the battery for preliminary experiments.

Example 1 A schematic cross-sectional view of the sample battery assembled in this example is shown in FIG. In FIG. 3, the positive electrode mixture (11) was composed of 88.9 parts by weight of manganese dioxide (Material F), 9.3 parts by weight of graphite, and 1.8 parts by weight of polytetrafluoroethylene.
It was pressed into a disk with a diameter of 1.55 cm at a pressure of 5 ton / cm ² and is installed in a positive electrode can (12) made of nickel-plated stainless steel. Negative electrode mixture (13)
Is a lithium metal (13) with a diameter of 1.55 cm, which is crimped into a negative electrode can (14) made of nickel-plated stainless steel. The negative electrode capacity is matched with the positive electrode capacity obtained when discharging under a sufficiently light load. The positive electrode mixture (11) and metallic lithium (13) are superposed on each other via a polypropylene separator (15), and a positive electrode can (12) is inserted via a polypropylene gasket (16) whose surface is coated with asphalt. ), The gasket (16) is compressed between the gasket (16) and the negative electrode can (14) to maintain the airtightness inside the battery. The separator (15) is permeated with an electrolytic solution, and the electrolytic solution contains 0.5 mol / l of lithium perchlorate in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1. 0.2 g dissolved in a ratio was used.

A lithium-manganese battery having a diameter of 20 mm and a height of 3.2 mm was assembled according to the above-described structure, and this was used as a sample battery 1.

Example 2 A lithium manganese battery was assembled by the same method as in Example 1 except that Sample I was used as the positive electrode active material, and this was designated as Sample Battery 2.

Comparative Example 1 A lithium manganese battery was assembled in the same manner as in Example 1 except that Sample K was used as the positive electrode active material, and this was designated as Sample Battery 3.

FIG. 4 shows a discharge curve when a 300 Ω constant load discharge up to a final voltage of 2 V was performed at 20 ° C. using the obtained sample battery. As is clear from FIG. 4, the battery of the present invention has a longer discharge duration in heavy load discharge than the comparative battery.

Next, in a lithium-manganese battery using chemically synthesized manganese dioxide, the following experiment was conducted in order to study the weight ratio of the negative electrode active material to the weight of the positive electrode active material and determine an appropriate range.

Examination of Weight Ratio of Negative Electrode Active Material to Positive Electrode Active Material According to the structure of the sample battery shown in FIG.
A manganese battery was created. However, the positive electrode active material used was a commercially available chemically synthesized manganese dioxide having a specific surface area value of 63 m ² / g, and 0.985 g of this was used to form a disk of 1.65 cm in diameter and 1.8 mm in height at 5 ton / cm ² It was used after being pressure molded at a pressure of. In addition, the negative electrode can (14) weighs 0.058 g, diameter
Lithium metal (13) 1.55 cm thick and 0.58 cm thick is pressure bonded.

Using the positive electrode active material and the negative electrode active material described above, a diameter of 20 mm,
A sample battery having a height of 3.2 mm and a weight ratio of the negative electrode active material to the positive electrode active material of the battery of 0.007 to 0.08 was prepared.

These sample batteries will reach 2V at 21 ° C.
Two-hour intermittent 8 mA constant current discharge was performed every 24 hours, and the total discharge capacity was obtained from the integrated value of the elapsed time. FIG. 5 shows the relationship between the discharge capacity and the weight ratio of the negative electrode active material to the positive electrode active material obtained when discharging under the above-mentioned discharge conditions. As is clear from FIG. 5, when chemically synthesized manganese dioxide having a specific surface area of 63 m ² / g is used as the positive electrode active material,
In the weight ratio range of 0.055 to 0.067, which was previously considered optimal, the discharge capacity at high current density does not reach the maximum, and the weight ratio is 0.025.
It was found that a discharge capacity of about 100 mAH or more can be obtained when the value is up to 0.070. However, a discharge capacity of 110 mAH was achieved when the weight ratio was 0.030 to 0.054.

〔The invention's effect〕

As is clear from the above description, in the present invention, since chemically synthesized manganese dioxide having a large specific surface area is used as the positive electrode active material of the organic electrolyte battery, the electrochemical reaction area of the interface between the electrolytic solution and the positive electrode active material. Can be increased, the electrode reaction can be carried out smoothly, and the utilization rate of the positive electrode active material during heavy load discharge can be improved.

Therefore, in the battery of the present invention, it is possible to increase the discharge capacity at the time of heavy load discharge in which a high current of several mA to several tens mA is discharged.

Further, manganese dioxide synthesized by chemical synthesis has a very low material price, and thus the manufacturing cost of the battery can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a configuration example of an organic electrolyte battery prepared in a preliminary experiment. FIG. 2 is a characteristic diagram showing the capacity per volume of the positive electrode active material with respect to the specific surface area of manganese dioxide. FIG. 3 is a schematic cross-sectional view showing a constitutional example of the organic electrolyte battery prepared in the example to which the present invention is applied. FIG. 4 is a characteristic diagram showing the discharge characteristics of the example to which the present invention is applied in comparison with that of the comparative example. FIG. 5 is a characteristic diagram showing the relationship between the weight ratio of the positive electrode active material and the negative electrode active material and the discharge capacity. 1 ... Positive electrode mixture 2 ... Positive electrode can 3 ... Metallic lithium 4 ... Negative electrode can 5 ... Separator 6 ... Gasket

Claims (1)

(57) [Claims] 1. An organic electrolyte battery comprising a positive electrode active material mainly containing manganese dioxide, a negative electrode active material mainly containing lithium or a lithium alloy, and an organic electrolyte solution, wherein the manganese dioxide of the positive electrode active material has a specific surface area of 50 to 90 m. ² / g
Which is a chemically synthesized manganese dioxide, wherein the weight ratio of the negative electrode active material to the positive electrode active material is 0.030 to 0.054.