JPH0831318B2 - Organic electrolyte battery - Google Patents

Description

The present invention relates to an organic electrolyte battery in which Li is used for the cathode, manganese dioxide is used for the anode, and an organic solvent is used for the electrolytic solution. Relates to the improvement of the internal resistance of this type of battery.

[Outline of Invention]

The present invention is composed of a cathode containing Li as a main component, an anode containing Al, an anode mainly containing manganese dioxide, and an organic electrolyte, and in an organic electrolyte battery that is controlled by the anode, the ratio of the amounts of Li and Al constituting the cathode is expressed by the ratio t ₂ / t ₁ of the thickness t ₂ of the thickness t ₁ and Al in Li this t ₂ / t ₁ and x, when the weight ratio of manganese dioxide to Li a (Li / MnO ₂₎ is y , Y = 0.2x + 0.067 y = 0.2x + 0.080 By selecting the amounts of Li, Al and manganese dioxide to be contained in the region surrounded by x ≥ 0.03, the increase in internal resistance at the end of discharge can be suppressed, It aims to use the capacity of the battery effectively until the end.

[Conventional technology]

Using a large electronegativity of metallic lithium as the negative electrode active material, the organic electrolyte battery using manganese dioxide as the active material for the anode shows a high battery voltage of about 3 V because the electrode potential of the metallic lithium is extremely low. It is known as one of the batteries having a high energy density due to the large electric capacity per unit weight of metallic lithium. Then, in this type of battery, an organic solvent is used in the electrolytic solution, for example, one in which an electrolyte such as lithium perchlorate is dissolved in propylene carbonate is used, and since both lithium metal and manganese dioxide are extremely stable in this electrolytic solution,
The battery capacity does not decrease even after long-term storage, and the storage stability is very good.

Therefore, in recent years, the use of this organic electrolyte battery is expanding as a backup power source for electronic watches and IC memories that require long-term reliability.

By the way, in the above-described battery, conventionally, there is a drawback that the internal resistance of the battery increases with discharge, and further, the internal resistance of the battery similarly increases even when stored at high temperature, and its improvement is a major problem. There is. The increase in the internal resistance of the battery hinders the effective use of the battery.For example, when a large pulse current is taken at the end of discharge, the battery voltage is greatly decreased due to the high internal resistance, and the battery is used in a large current in pulses. Cannot use the capacity of the battery effectively until the end.

As a cause of such an increase in internal resistance, first of all, metallic lithium is generally stable in an organic electrolytic solution, but it is very active, so that it is accompanied by discharge progress or during storage at high temperature. It is considered that the surface of the metallic lithium gradually reacts with the organic electrolytic solution to form an inactive compound film on the surface.

In this case, the amount of reaction has almost no influence on the capacity of the battery, but the formed film on the surface of lithium greatly hinders the anode reaction of lithium. For this reason,
This causes an increase in the internal resistance of the battery.

Therefore, in order to eliminate such drawbacks, for example, it is proposed to use a lithium-aluminum alloy in U.S. Pat. No. 4,024,492 and U.S. Pat. Has not been obtained.

Generally, the discharge reaction of a lithium battery using manganese dioxide as an anode active material is proposed to be Mn ^IV O ₂ + Li → Li ⁺ Mn ^III O ₂ .

In such a lithium battery, during discharge, lithium in the negative electrode is transferred to the positive electrode, and the discharge product increases in the positive electrode along with the discharge to increase the internal resistance. Further, due to the migration of the cathode lithium, the facing area of the lithium electrode decreases at the end of discharge, causing a sharp increase in internal resistance.

[Problems to be solved by the invention]

Thus, in the conventional organic electrolyte battery, an increase in internal resistance at the end of discharge is unavoidable, which is a great obstacle to effective use of the battery.

Therefore, the present invention has been proposed in order to solve the drawbacks of the above-mentioned conventional organic electrolyte battery, suppresses the increase in internal resistance at the end of discharge, expands the region where internal resistance is suppressed, It is an object of the present invention to provide an organic electrolyte battery that can effectively utilize the capacity it has until the end.

[Means for solving problems]

The present inventor has conducted extensive research over a long period of time with the aim of improving the resistance characteristics of the organic electrolyte battery, and by using lithium containing aluminum for the cathode, suppresses surface deactivation and suppresses an increase in internal resistance. Further, it has been found that by setting the amounts of lithium and aluminum and manganese dioxide used for the anode within a predetermined range, it is possible to widen the region where the internal resistance is suppressed.

It is composed of a cathode containing Li as a main component, an anode containing Al, an anode mainly containing manganese dioxide, and an organic electrolytic solution, and the capacity of the cathode Li is set to be larger than the capacity of the anode.
The ratio of the amount of Al to the thickness of Li t ₁ and the ratio of the thickness of Al t ₂ t ₂ / t ₁
Where t ₂ / t ₁ is x and the weight ratio of manganese dioxide to Li (Li / MnO ₃ ) is y, it is surrounded by y = 0.2x + 0.067 y = 0.2x + 0.080 x ≧ 0.03 It is characterized in that the amounts of Li, Al and manganese dioxide are selected so as to be included in the region.

In the organic electrolyte battery of the present invention, for example, as shown in FIG. 1, metal lithium (2) having an aluminum foil (1) attached to the surface is used as a cathode active material, and manganese dioxide pellets (3) such as electrolytic manganese dioxide are used. Is used as the anode active material, and these are filled in the cathode can (5) and the anode can (6) through the separator (4) containing the organic electrolyte. As the organic electrolytic solution, generally, propylene carbonate, butyrolactone, tetrahydrofuran, 1,2-dimethoxyethane, 1,3-dioxolane, etc., or a mixed solvent of two or more kinds, and an electrolyte such as lithium perchlorate or lithium borofluoride. What melt | dissolved etc. is used.

Here, first, in the cathode active material, the ratio of the amount of metallic lithium (2) to the amount of aluminum foil (1) is important, and the thickness of metallic lithium (2) is t ₁ , and the aluminum foil ( When the thickness of 1) is t ₂ , these ratios t ₂ / t
₁ (hereinafter, referred to as x) is preferably 0.03 or more. If this value is less than 0.03, that is, if the amount of lithium is too large, the increase in internal resistance cannot be sufficiently suppressed. Further, if the value of x is 0.03 or more, the internal resistance at the end of discharge is suppressed, but if it is too large, that is, if the amount of aluminum is too large, the electric capacity may decrease. Although the details of this cause are unknown, metallic lithium diffuses into the aluminum foil attached to the lithium, and the aluminum foil is
This is considered to be because Li-Al alloy is formed, and Li that cannot directly contribute to the battery reaction is generated. Therefore, as a practical range, 0.03 ≦ x ≦ 0.10.

In this example, the aluminum foil is attached to the surface of metallic lithium, but aluminum may be contained in the state of alloy on the surface of lithium. Also in this case, the amount of aluminum may be such that the composition corresponds to the thickness ratio as described above.

On the other hand, as described above, when aluminum is contained on the surface of metallic lithium that is a cathode active material, the substantial amount of lithium involved in the battery reaction is reduced. Therefore, in order to expand the region where the internal resistance is suppressed, the capacity of the cathode lithium is larger than the capacity of the cathode, that is, the anode is dominant,
Further, the weight ratio of lithium to manganese dioxide needs to be optimized in consideration of the content of aluminum.

According to the experiments conducted by the present inventor, there is a correlation between the lithium-to-aluminum ratio x and the lithium-to-manganese dioxide weight ratio y, which are y = 0.2x + 0.064 to y = 0.2x + 0.067. It was found that the cathode and the anode had the same capacity in the region of 1 and the battery capacity had the maximum value. In the present invention, from the viewpoint of controlling the anode, y ≧ 0.2x + 0.067. That is, as the weight ratio y of lithium and manganese dioxide increases, the cathode capacitance increases and the region where the internal resistance is suppressed expands. However, as the weight ratio y increases, the battery capacity tends to decrease, and in practical terms, y ≦ 0.2x + 0.080 is preferable from the viewpoint of discharge capacity.

The amount of manganese dioxide is the weight of the commercially available electrolytic manganese dioxide obtained by heat treatment at 200 to 600 ° C.

[Action]

Thus, while using metallic lithium containing aluminum as the cathode active material of the organic electrolyte battery, the ratio of the amount of aluminum and the amount of lithium is set within a predetermined range,
By setting the ratio y of the amount of lithium and the amount of manganese dioxide of the anode to a predetermined range corresponding to the ratio x of the amount of aluminum and lithium, inactivation of the cathode surface is prevented and increase in internal resistance is suppressed. In addition, the area where the internal resistance is suppressed is expanded.

〔Example〕

Experimental Example 1 To 88.9 parts by weight of commercially available electrolytic manganese dioxide heat-treated at 300 ° C. for about 5 hours, 9.3 parts by weight of graphite was added, and further, 1.8 parts by weight of polytetrafluoroethylene (trade name Teflon) was added as a binder. To obtain an anode mix, which was molded into a diameter of 15.5 mm and a weight of 0.655 g to prepare anode pellets.

Next, a 0.40 mm thick lithium foil is punched to a diameter of 15.5 mm and attached to an anode cup, and an aluminum foil with a thickness of 0.007 mm to 0.06 mm is punched and pressed onto this lithium foil. Then, they were bonded together to form a lithium cathode.

In addition, place a separator on this lithium cathode, insert a plastic gasket, and use 1Mol as an electrolyte.
Inject propylene carbonate in which / LiClO ₄ was dissolved, put the above anode pellets and cover with a cathode can,
After sealing, an organic electrolyte battery as shown in FIG. 1 was assembled.

Here, the sample with an Al / Li thickness ratio of 0.00175 is Sample 1.0.
The sample of 037 was sample 2, the sample of 0.074 was sample 3, the sample of 0.112 was sample 4, and the sample of 0.150 was sample 5.

In addition, an organic electrolyte battery was assembled in the same manner as each of the above samples without attaching the aluminum foil, and this was used as a comparative example.

Changes in the internal resistance of each of the above-mentioned samples and comparative examples were examined. Results are shown in FIG.

From this FIG. 2, it was found that the lithium cathode battery to which the aluminum foil was attached had a much lower internal resistance than the comparative example, and the internal resistance did not change much during discharge and storage.

In order to clarify this tendency, the relationship between the Al / Li thickness ratio and the internal resistance of the battery after 80% discharge was investigated. Results are shown in FIG. It can be seen from FIG. 4 that the internal resistance sharply decreases as the Al content increases.

However, the following defects were discovered by this alone. That is, in a battery in which an aluminum foil is attached to lithium, as the Al / Li thickness ratio increases, the internal resistance becomes low and the resistance change during discharge is small, as shown in FIG. As shown in FIG. 3, the electric capacity decreases conversely, and the amount of decrease decreases as the Al / Li thickness ratio increases.

Therefore, in an organic electrolyte battery with a lithium cathode attached to an aluminum foil, the weight ratio of Li / MnO ₂ is Al
It is necessary to take into consideration the content of.

Therefore, the present inventor found the appropriate weight ratio of Li / MnO ₂ of the organic electrolyte battery having lithium as a cathode to which an aluminum foil was attached as the cathode by the following experiment.

Experimental Example 2 From Experimental Example 1, it was found that the preferable internal resistance value (15Ω or less) up to 80% discharge was that the Al / Li thickness ratio was 0.03 or more.

Therefore, aluminum foils of various thicknesses were attached to the anode-up lithium foils, and Al / Li thickness ratios of 0.03 to 0.10.

Furthermore, as anode pellets, various weights of MnO ₂ (30
Heat treatment for 4 hours at 0 ℃)
Similarly to the above, an organic electrolyte battery having a structure as shown in FIG. 1 was assembled. However, the outer diameter of the battery was set to 20 mm and the height was set to 2.45 mm.

Each of the obtained batteries had an Al / Li thickness ratio of 0.03 to 0.10.
And the Li / MnO ₂ weight ratio was from 0.60 to 0.90.

Each of these batteries was discharged with a constant resistance of 3 KΩ, and the capacity was measured. The results are shown in the table below.

In this table, the numbers in parentheses show the case where the capacity of the anode is larger than the capacity of the cathode lithium, that is, the battery is controlled by the cathode, and in this case, the region where the internal resistance is suppressed is narrow.

The inventor of the present invention has shown that among the samples in the above table, the sample having the Al / Li thickness ratio x of 0.05 and the Li / MnO ₂ weight ratio of y of 0.065 was sample 6, and the sample having y of 0.07 was sample 7. , y is 0.076
Samples 9 having 8, y of 0.082 were examined for changes in internal resistance and discharge characteristics. The change in internal resistance is shown in FIG. 5, and the discharge characteristic is shown in FIG. In addition,
Sample 6 is a cathode-dominated battery.

From FIG. 5 and FIG. 6, in the sample 6 which is a cathode-dominated battery, the region where the internal resistance is suppressed is narrow,
From the viewpoint of effective utilization of battery capacity, each sample of the present invention (Sample 7
And was found to be disadvantageous compared to sample 8).

From the above experimental results, the present inventor has come to the following conclusions. That is, from the above table, the Al / Li thickness ratio x and the Li / MnO ₂ weight ratio y are y = 0.2x + 0.064 to y = 0.2x + 0.
067 has the maximum battery capacity. Therefore, if at least y ≧ 0.2x + 0.067, it is considered that the battery is controlled by the anode, and the region where the internal resistance is suppressed becomes wide. This is also confirmed from FIGS. 5 and 6. On the other hand, from the above table, y ≧ 0.2x + 0.06
In the region of 7, the battery capacity decreases as the Li / MnO ₂ weight ratio y increases. Therefore, considering a practical range, y ≦ 0.2x + 0.080 is preferable.

From these experimental results, the range of the present invention is a region surrounded by y = 0.2x + 0.067 y = 0.2x + 0.080. If this is illustrated, the area shown by the diagonal lines in FIG.

〔The invention's effect〕

As is clear from the above description, in the organic electrolyte battery of the present invention, the metallic lithium containing aluminum is used for the cathode, and the lithium amount and the manganese dioxide amount of the anode are set in consideration of the aluminum content. Therefore, the internal resistance is very small.

Further, the organic electrolyte battery of the present invention has a wide area where the internal resistance is suppressed, and the capacity of the battery can be effectively utilized to the end.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an organic electrolyte battery according to the present invention. FIG. 2 is a characteristic diagram showing a change in internal resistance with a change in the Al / Li thickness ratio, and FIG. 3 is a characteristic diagram showing a change in a discharge voltage curve with a change in the Al / Li thickness ratio. is there. FIG. 4 is a characteristic diagram showing the relationship between the Al / Li thickness ratio and the internal resistance value at 80% discharge. FIG. 5 is a characteristic diagram showing changes in internal resistance with changes in the Li / MnO ₂ weight ratio when the Al / Li thickness ratio is constant,
FIG. 6 is a characteristic diagram showing changes in the discharge voltage curve with changes in the Li / MnO ₂ weight ratio. Fig. 7 shows the preferable range in terms of internal resistance and battery capacity
The ratio of the thickness of the Al / Li (x) and Li / MnO ₂ weight ratio is a characteristic diagram showing a relationship (y). 1 …… Aluminum foil 2 …… Metallic lithium 3 …… Manganese dioxide pellets 4 …… Separator

Claims (1)

[Claims] 1. A cathode comprising Li as a main component and Al as a main component, an anode mainly as a manganese dioxide, and an organic electrolyte, wherein the capacity of the cathode Li is larger than the capacity of the anode, and the Li constituting the cathode is formed. The ratio of the amount of Al to the thickness of Li t ₁ and
Representing the ratio t ₂ / t ₁ of the thickness t ₂ of Al, where t ₂ / t ₁ is x, and the weight ratio of manganese dioxide to Li (Li / MnO ₃ ) is y, y = 0.2x + 0. An organic electrolyte battery characterized in that the amounts of Li, Al and manganese dioxide are selected so that they are contained in a region surrounded by y = 0.2x + 0.080 x ≧ 0.03.