JPH0744032B2 - Method for manufacturing organic electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electrolyte battery (so-called lithium primary battery) using lithium as a negative electrode active material and an organic electrolytic solution as an electrolytic solution, and particularly to manganese dioxide. The present invention relates to an improvement in a method for manufacturing an organic electrolyte battery using as a positive electrode active material.

[Summary of the Invention] The present invention is solved by adding LiMnO ₂ in the positive electrode active material (manganese dioxide) of an organic electrolyte battery without discharging the high-potential portion immediately after battery assembly, and is desired from the beginning. The present invention is intended to obtain a method for manufacturing an organic electrolyte battery exhibiting the battery potential of

[Conventional technology]

An organic electrolyte battery (so-called lithium primary battery), which uses metallic lithium as a negative electrode and an organic electrolyte as an electrolyte, has excellent storage stability and extremely high performance, and is useful as a substitute for other primary batteries. It is attracting attention as a battery.

The organic electrolyte battery is used as a power supply battery for a clock, a camera, a calculator, a memory backup, etc.

As a practical example of the organic electrolyte battery used as a power supply battery for various consumer electronic devices as described above, for example, a combination of Li / MnO ₂ , Li / CF _x , Li / SOCl _2, etc. It is known that, in particular, a combination of Li / MnO ₂ is produced and used in large numbers because of its advantages of high load characteristics and low cost of raw materials.

However, the above-mentioned organic electrolyte battery made of Li / MnO ₂ exhibits a very high potential of 3.5 to 3.6 V immediately after the battery is assembled and processed. It is said that this is because manganese dioxide used as the positive electrode active material has a portion exhibiting extremely high activity.

When such a highly active portion is present in the anode can,
As a result, the organic electrolytic solution used as the electrolytic solution is deteriorated and the storability of the battery is deteriorated.

Further, electronic components such as ICs incorporated in various consumer electronic devices that use the organic electrolyte battery, since the allowable range of the operating potential is generally around 3.3V, the organic electrolyte showing the high potential. If the battery is installed in the device as it is, abnormal display or malfunction may occur, and further, electronic parts may be damaged.

Therefore, as a countermeasure, it has been proposed and tried to add an additive to manganese dioxide used in the positive electrode active material, or to subject the manganese dioxide itself to a special treatment. Has not been done. Therefore, at present, after producing the organic electrolyte battery exhibiting the above-mentioned high potential, a part of the battery capacity is intentionally discharged to reduce the potential to a desired potential. However, the above-mentioned discharge treatment work poses a serious problem in terms of the battery processing process or productivity.

[Problems to be solved by the invention]

As described above, the organic electrolyte battery made of Li / MnO ₂ exhibits a very high potential immediately after the battery is assembled and processed, so that part of the battery capacity is intentionally discharged to reduce the battery potential to a desired potential. I am letting you.

However, the above-mentioned discharge treatment work poses a serious problem in terms of the battery processing process or productivity, and it is desired to assemble and process the organic electrolyte battery without performing the above-mentioned discharge treatment work.

Therefore, the present invention has been proposed in view of the above circumstances, and an object thereof is to provide an organic electrolyte battery exhibiting a desired battery potential even immediately after battery assembly, and a part of the capacity of the battery after battery production. It is an object of the present invention to provide a method for producing an organic electrolyte battery having excellent productivity, which does not require intentional discharge treatment.

[Means for solving problems]

The present inventors, as a result of extensive research over a long period of time to achieve the above-mentioned object, that the addition of LiMnO ₂ is effective in eliminating the initial high potential portion of the organic electrolyte battery using manganese dioxide as a positive electrode active material. Heading The present invention has been completed. That is, the present invention, when manufacturing an organic electrolyte battery composed of a negative electrode active material mainly composed of lithium or a lithium alloy, a positive electrode active material mainly composed of manganese dioxide, and an organic electrolytic solution, LiMnO _{2 is} previously added to the positive electrode active material. Is added.

[Action]

By adding LiMnO ₂ to manganese dioxide used as a positive electrode active material of an organic electrolyte battery, an initial high potential portion immediately after battery assembly is removed without performing discharge treatment.

The details of the role that LiMnO ₂ plays in the positive electrode active material are unknown, but it is speculated as follows.

First, as a result of studying the mechanism for lowering the battery potential in the discharge treatment that has been conventionally performed immediately after battery assembly, a small amount (x amount) of LiMnO ₂ was observed on the surface of the positive electrode mixture immediately after this discharge treatment.
It was found that (xLiMnO ₂ ) was formed.

This xLiMnO ₂ probably reacts with MnO ₂ as follows.

_{(1-x) MnO 2 +} xLiMnO 2 → Li x MnO 2 i.e., the discharge reaction in MnO _2, occur charge reaction in LiMnO _2, the entire positive electrode mixture becomes homogeneous Li _x MnO _2. As a result, the high potential part of the entire MnO ₂ disappears.

On the other hand, if LiMnO ₂ is added to MnO ₂ in advance,
Li _x MnO ₂ which reacts with O ₂ and is uniform throughout the positive electrode mixture
And the high potential part of the entire MnO ₂ disappears. Therefore, excellent preservability can be obtained without performing discharge treatment immediately after battery assembly.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, a preliminary test was conducted to clarify what kind of reaction occurred in the battery when the high potential portion was removed by intentional discharge.

Preliminary Test The following lithium / manganese dioxide battery was made to perform a test to remove the high potential portion of the assembled battery.

Metal lithium was used for the negative electrode, and manganese dioxide, graphite, and polytetrafluoroethylene were mixed for the positive electrode at a ratio of 88.9: 9.3: 1.8 (numerical values represent parts by weight), and the diameter was 15.5 mm. Thickness 1.65mm, weight 0.894g
Pellets that were pressure-molded into were heat-treated. A polypropylene non-woven fabric was used as the separator, and a non-aqueous electrolyte prepared by dissolving 1 mol / l of LiClO ₄ in a mixture of propylene carbonate and dimethoxyethane at a volume ratio of 1: 1 was used as the electrolyte.

Using these materials, as shown in FIG. 1, metallic lithium (4) is pressure-bonded to an anode cup (1) as a cathode material, and a separator (3) containing an electrolytic solution is further placed on the anode cup (1) to form a plastic. After fitting the gasket (6) of the above, put the prepared positive electrode pellet (5) on the separator (3) and cover the cathode can (2), and seal the end by caulking the outer diameter 20mm, total height A 3.2 mm organic electrolyte battery was assembled. The anode cup (1) and the cathode can (2) were made of nickel-plated stainless steel.

The organic electrolyte battery thus assembled exhibited a high potential of 3.56 V immediately after assembly. Therefore, replace the above battery with 2
Individual pieces were prepared and each was subjected to preliminary discharge for 8 minutes with a load resistance of 30Ω to remove the high potential portion. The battery potential immediately after discharging the above load resistance of 30Ω for 8 minutes was 1.2 to 1.3V.

After the preliminary discharge, one of the batteries was immediately disassembled, the positive electrode pellet was taken out, and the X-ray diffraction analysis on the positive electrode pellet was performed. The diffraction pattern of this X-ray diffraction analysis is shown in FIG.

The other battery was stored at room temperature for 1 day after preliminary discharge, decomposed, taken out from the positive electrode pellet, and subjected to X-ray diffraction analysis on the positive electrode pellet. The diffraction pattern of this X-ray diffraction analysis is shown in FIG. The potential of this battery was 3.2 V, and the potential had recovered to a desired value after being stored for 1 day.

As a result, from the X-ray diffraction pattern on the positive electrode pellet of the battery immediately after discharging for 8 minutes with the load resistance of 30Ω, the peak of manganese dioxide was mixed and the LiMnO ₂
A peak matching with was found. However, from the X-ray diffraction pattern on the positive electrode pellet of the battery shown in FIG.
No peak that could be LiMnO ₂ was found.

From the above results, the present inventors have found that in a battery under heavy load discharge, a layer of LiMnO ₂ is formed in the positive electrode pellet, and after heavy load discharge, the layer is gradually oxidized by the highly active portion in the positive electrode pellet. The mechanism was presumed that LiMnO ₂ disappears and takes the form of Li _(1-x) MnO _2, and the active part in the positive electrode pellet also disappears.

Therefore, it is expected that the high potential after battery assembly can be eliminated by adding an appropriate amount of LiMnO ₂ to the mixture forming the positive electrode pellets in advance.

Based on the results obtained from the above preliminary tests, it is expected that LiMnO ₂ will be effective in eliminating the high potential of the assembled cell. Therefore, LiMnO ₂ was actually added to fabricate an organic electrolyte.

Example 1 In this example, LiMnO ₂ was obtained by electrochemically reacting lithium and manganese dioxide in an organic electrolyte.

The LiMnO ₂ thus obtained is mixed with a positive electrode mixture, that is, manganese dioxide, graphite, and polytetrafluoroethylene at a ratio of 88.9: 9.3: 1.8 (the values represent parts by weight). A mixture of 9 parts by weight with respect to was used as a new positive electrode mixture, which had a diameter of 6.85 m.
The positive electrode pellet was obtained by pressure molding into m, thickness 1.81 mm, and weight 0.197 g.

This positive electrode pellet was attached to the battery shown in FIG.
A sample battery with a height of 3 mm and a total height of 3 mm was assembled. This was designated as Battery A.

Also, compare batteries similar to those used in the preliminary test, that is, batteries using the positive electrode mixture with the composition of manganese dioxide: graphite: polytetrafluoroethylene = 88.9: 9.3: 1.8 as the positive electrode pellets. As an example, it was assembled in the same manner as Battery A.

FIG. 4 shows changes in the battery potential immediately after the battery A and the comparative example were assembled. The battery potential of the battery A is 0.4V lower than that of the comparative example.

After assembling the above comparative example, a high potential was removed by discharging with a load resistance of 30Ω for 10 minutes. And the potential that battery A showed is 3.12V
The potential was dropped to.

As described above, the battery A having a substantially equal potential and the comparative example 60
Changes in the properties of the ones stored in a constant temperature bath at ℃ for 20 days were measured. The results are shown in Table 1.

The battery A showed no increase in potential after storage at 60 ° C. for 20 days, and showed excellent characteristics equal to or higher than those of the comparative example subjected to the discharge treatment.

Example 2 In Example 1, it was confirmed that by adding an appropriate amount of electrochemically synthesized LiMnO ₂ to the positive electrode mixture, it was effective in removing the high potential portion. So easier and cheaper
As a method for synthesizing LiMnO ₂ , a chemical synthesis method was studied.

Electrolytic manganese dioxide and lithium carbonate are mixed in a ratio of 1: 2 (molar ratio), and the mixture is mixed in an inert gas atmosphere at 800 to 950 ° C for 3 times.
LiMnO ₂ was synthesized by firing for a period of time. As a result of X-ray diffraction analysis of the LiMnO ₂ obtained here, the pattern shown in FIG. 5 was obtained, and it was confirmed to be LiMnO ₂ .

LiMnO ₂ obtained by the above chemical synthesis was mixed with a positive electrode mixture of an organic electrolyte battery, that is, manganese dioxide, graphite and polytetrafluoroethylene at a ratio of 88.9: 9.3: 1.8 (numerical values represent parts by weight). A sample battery was assembled in the same manner as in Example 1 above, using a mixture of 9 parts by weight of the above mixture as a new positive electrode mixture. This was designated as Battery B. In addition, the battery similar to that assembled in the preliminary test, that is, the composition of the positive electrode mixture was manganese dioxide: graphite: polytetrafluoroethylene =
A battery in which a ratio of 88.9: 9.3: 1.8 was used as a positive electrode pellet was assembled as a comparative example.

After assembling the above battery B, the change in the battery potential was measured in the same manner as in Example 1. The result is shown in FIG. Battery B
The battery potential of No. 2 was 0.2 V lower than that of Comparative Example.

Further, the change in the characteristics of the battery B and the comparative example stored in a constant temperature bath at 60 ° C. for 20 days as in Example 1 were measured. The results are shown in Table 2.

The battery B showed no increase in the potential after being stored at 60 ° C. for 20 days and showed a tendency to decrease on the contrary, and exhibited the same or better characteristics as compared with the comparative battery subjected to the discharge treatment. Indicated.

Therefore, it is judged that LiMnO ₂ obtained by the chemical synthesis is also effective in removing the high potential part.

(Effects of the Invention) By adding LiMnO ₂ to manganese dioxide used as a positive electrode active material of an organic electrolyte battery, it becomes possible to provide an organic electrolyte battery exhibiting a desired potential even immediately after battery preparation, whereby It is possible to omit the processing work of intentionally discharging a part of the capacity of the battery.

Therefore, the processing steps of the battery are simplified and the productivity is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an organic electrolyte battery to which the present invention is applied. FIG. 2 is a characteristic diagram showing an X-ray diffraction spectrum of the positive electrode pellet after the preliminary discharge, and FIG. 3 is a characteristic diagram showing an X-ray diffraction spectrum of the anode pellet left for one day after the preliminary discharge, and FIG. Fig. 5 is a characteristic diagram showing the change with time in the potential of a battery in which electrochemically synthesized LiMnO ₂ was added to the positive electrode pellet, compared with that of the comparative example. Fig. 5 shows the X-ray diffraction of chemically synthesized LiMnO ₂ FIG. 6 is a characteristic diagram showing a spectrum, and FIG. 6 is a characteristic diagram showing changes in potential with time in a battery in which LiMnO ₂ obtained by chemical synthesis is added to a positive electrode pellet, as compared with that in a comparative example. 4 ... Metallic lithium (negative electrode active material) 5 ... Positive electrode pellet (positive electrode active material)

Claims (1)

[Claims] 1. When manufacturing an organic electrolyte battery comprising a negative electrode active material mainly composed of lithium or a lithium alloy, a positive electrode active material mainly composed of manganese dioxide, and an organic electrolytic solution, LiMnO _{2 is} previously added to the positive electrode active material. A method for producing an organic electrolyte battery, which comprises adding