JPS58161253A - Manufacture of positive pole active substance for cell - Google Patents

Abstract

PURPOSE:To produce a highly reliable cell having high voltage and high energy density, by cleaning chrome intermediate oxide or Cr3O8 with pure water then thermally processing under the temperature of 150-300 deg.C to produce the positive pole active substance. CONSTITUTION:A positive pole current collector 6 and a positive pole 5 are contained in a case 7 then a negative pole 2 composed of metal lithium is provided through a polypropylene unwoven separator 3 and sealed through a seal board 1 and a synthetic resin gasket 4. Intermediate oxide or Cr3O8 is employed for the positive pole 5 where Cr3O8 is immersed in pure water of approximately 10 times volume then agitated and filtered after 10-20min later then cleaned and thermally processed under the temperature of 150-300 deg.C. The thermally processed Cr3O8 is mixed with acetylene black as the conductive material and fluoride resin as a binder then pressure molded. The electrolyte is a mixed solvent of propylene caronate and dimethoxy ethane dissolved with lithium perchlorate. When employing a positive pole active substance processed in such a manner, a highly reliable cell having high voltage and high energy density can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery, particularly a battery using C technology, in which a light metal such as an alkali metal or an alkaline earth metal is used as a negative electrode active material, an organic electrolyte is used as an electrolyte, and a chromium intermediate oxide is used as a positive electrode active material. The present invention relates to a method for producing a positive electrode active material for an organic electrolyte battery using No. 08, and aims to provide a battery with high voltage, high energy density, and high reliability.

To date, various metal oxides have been measured and studied as positive electrode active materials for organic electrolyte batteries, and the ones that have been put into practical use include 21.21.dioxide, manganese (MnO2), and chromic acid. Silver (A92cro4)
.

Copper oxide (CuO), bismuth trioxide (B1203).

There are bismuth copper composite oxides (B, 2Cu04), etc., which are all combined with a lithium negative electrode and are known as lithium batteries.

Regarding chromium oxide, U.S. Patent No. 3.415
, 687, when chromium trioxide (CrO3) is used as a positive electrode active material in combination with a lithium negative electrode, 3.6
It is described that it exhibits an open circuit voltage of 8V, and in German Patent No. 2,341,723, a graphite intercalation compound (C8Cr03) is described as a positive electrode active material for secondary batteries in combination with an alkali metal. ing. Furthermore, chromium intermediate oxides Cr3O8 and Cr206, together with thermal decomposition products of CrO3 alone or with graphite, are organic electrolyte systems, and when combined with a lithium negative electrode, are very useful in primary and secondary batteries. It is known that it can be used as a positive electrode active material.

In particular, the present inventors have discovered that Cr3O, which is a chromium intermediate oxide,
As a result of a detailed study regarding No. 8, we found that the characteristics of this type of battery are greatly affected by the cathode manufacturing method. That is, Cr3O8 is generally obtained by thermal decomposition of chromium trioxide (CrO3), but some unreacted chromium trioxide (CrO3) remains.

This CrO3 is not only highly water-absorbing, but also highly toxic. In organic electrolyte batteries using an alkali metal as a counter electrode, water is a major impediment to the long-term reliability of the battery and must be eliminated. Furthermore, since CrO3 has low solubility in organic solvents, there is a high possibility that dissolved hexavalent chromium ions (C'') will precipitate on the alkali metal surface, impairing the reliability of the battery. The present invention selects a cleaning method using pure water or alcohol as a method for effectively removing this CrO3, and performs a heat treatment at an appropriate temperature of 150 to 300'C after cleaning. It provides a battery with high density and high reliability.

1. The present invention will now be explained in detail by way of examples thereof.

The positive electrode active material Cr3O8 is commercially available chromium trioxide (Cr
03) was prepared by heat treatment at an oxygen pressure of 20 atmospheres and a temperature of 250''C for 12 hours.The obtained Cr3O8 was then subjected to various treatments as shown in Table 1.

For washing, the sample was immersed and stirred in about 10 times the volume of pure water, alcohol, and ethanol, and filtered after about 10 to 20 minutes. In the case of alcohol, since the color changes to brown immediately after dipping, the dipping time was set to about 10 minutes. The residue becomes slightly sticky. This discoloration is thought to be due to the oxidation reaction of alcohol to aldehyde and the dissolution of hexavalent chromium ions < cr6 + ).

Table 1 6'' The dissolution of hexavalent chromium ions was confirmed by the fact that when water was added to the alcohol filtrate, a yellowish tint appeared.On the other hand,
In the case of pure water, the color changes to bright yellow due to the dissolution of hexavalent chromium ions. The filtration residues were each washed with the same pure water or alcohol as the immersion liquid, and then heat-treated at each temperature shown in Table 1 for 12 hours. The atmosphere was normal pressure air. No change in appearance of Cr308 was observed after heat treatment.

FIG. 1 is a cross-sectional view of a flat battery used for evaluation. In the figure, 1 is a sealing plate, 2 is metal lithium as a negative electrode, 3 is a polypropylene nonwoven fabric separator, and 4 is a synthetic resin gasket. 5 is a positive electrode, which is composed of untreated or treated Cr3o8, an acetylene blank as a conductive material, and a fluororesin as a caking material in a weight ratio of 10.
:1:1 mixture was pressure-molded into a diameter of 14 mm and a thickness of 0.6 mm. 6 is a positive electrode current collector;
7 is a case. The electrolyte was a mixture of propylene carbonate and demethine ethane in a weight ratio of 1:1 in a six-base medium, and 1 mol/LV of lithium perchlorate was used as the electrolyte.

A solution dissolved at the following ratio was used.

Shida. Symbols 1 to 8 in the figure correspond to each Cr308 of processing examples 1 to 8 in Table 1, respectively. As is clear from Figure 2, C
It can be seen that R3084 and Samples 7 and 8, which were heat treated at 260''C after alcohol cleaning, exhibit better discharge characteristics than untreated sample 1 even immediately after assembly.15
Product 3 heat-treated at 0''C shows good characteristics, although its discharge capacity is slightly inferior.Product 6 heat-treated at 3o'C shows deterioration in characteristics, and product 6 treated at 35o'C% shows a more pronounced deterioration. On the other hand, product 2 treated at a low temperature of 1o○°C hardly shows any discharge capacity.
From the comparison of 8, the cleaning solution for removing Cr03 is:
Pure water is considered the most suitable.

1 Alcohol cleaning removes CrO3 and also removes alcohol.
Because side reactions such as oxidation of old chlorine occur, it is unclear in terms of cleaning system, but it is inferior to water cleaning in terms of capacity. The reason why the characteristics deteriorate with heat treatment above 30o'C is thought to be due to the formation of lower chromium oxides such as CrO2, and the discharge characteristics, which are the two-step curve shown in Figure 2, also deteriorate. This is consistent with this idea. 150-30
The reason for the improvement in discharge performance by heat treatment at 0''C, particularly preferably at 250°C, is unknown, but in terms of X-ray diffraction, the diffraction peak of C73o8 becomes unclear and amorphous broad peaks are formed. From the above, in the case of C7308, an amorphous structure is preferable in terms of discharge mechanism, so it is thought that the utilization rate will improve.In addition, the remaining unreacted CrO3 is completely decomposed into Cr3O8, increasing the purity. It is also thought that the discharge capacity increased because the discharge capacity improved.

Regarding the reliability of the battery, we estimated the degree of gas generation inside the battery from the swelling of the battery's total height after two weeks.
In addition, discoloration due to the precipitation of chromium-poor ions on the lithium surface was investigated through a decomposition investigation focusing on abnormal battery voltage and internal resistance, and the results are shown in Table 2.

In case 2, which was heat-treated at 1 oO'C after the second surface water washing, a large amount of water was clearly contained in the positive electrode, and more than half of the 40 samples generated gas inside the battery. Also,
It can be seen that even in the untreated product 1, about 20 cells were generating gas internally. On the other hand, after cleaning, 160°
In Nos. 3 to 8, which were subjected to heat treatment of C or higher, no swelling of the battery was observed, indicating that dehydration was sufficiently performed. In addition, no discoloration of the surface of the lithium negative electrode of the batteries was observed in 9 H in Nos. 3 to 6 and No. 7, and no abnormalities were observed in the voltage or internal resistance of the batteries using Cr3O8 as the positive electrode active material. It can be seen that according to the present invention, CrO3 is sufficiently removed and reliability is high.

By adopting the method of the present invention as described above, high voltage,
A battery with high energy density and high reliability can be provided.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a flat battery used to evaluate the characteristics of the present invention, and Figure 2 is a Cr3 battery that has been subjected to various treatments according to the present invention.
FIG. 3 is a diagram showing the discharge characteristics of a battery using O8 as a positive electrode. 2-negative electrode, 3- separator, 6...pressure-molded positive electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 ``E arrow mark stitching (eaves)

Claims (2)

[Claims] (1) After cleaning Cr3O8, which is chromium intermediate oxide, 1
A method for producing a positive electrode active material for a battery, comprising heat treatment at a temperature of 5o to 300°C. (2) The method for producing a positive electrode active material for a battery according to claim 1, wherein the Cr3O8 cleaning liquid is pure water.