DE3513119A1 - Process for preparing higher-valence nickel oxides for electrical accumulators in a chemical manner - Google Patents

Abstract

The process utilises the reactivity of amorphous, non-magnetic nickel powder to be converted directly, by oxidation with ozone, into higher-valence, electrochemically active nickel oxides. The reaction medium used for this purpose is an aqueous alkaline solution of single or mixed alkali metal hydroxides. The reaction takes place at a pH greater than 8. Good mixing of the reactants is ensured by stirring or vibration. The reaction proceeds at room temperature and, if suitable equipment is used, achieves nearly 100%.

Description

"Process for the production of higher quality nickel oxides for electrical

Accumulators by chemical means. "It exists on the part of the battery industry a sustained interest, equal to the wet electrochemical forming process for which electrode shape or for which battery system to refrain.

The wet formation is a technical one in every accumulator production necessary but always unpleasant work phase. Also in terms of environmental pollution the forming device gives cause for criticism again and again. For negative electrodes both in lead battery production and more alkaline for certain cadmium electrodes The problem is not so serious for accumulators because it is possible is, the minus mass from the outset in the metallic, i.e. electrochemically active To bring the state into the current discharge framework. For the positive electrodes are to date no usable methods known that allow the positive mass to be chemically oxidized separately prior to introduction into the electrode holder, with which both polarities of the battery would be available dry precharged.

The invention described below relates to a Possibility of specifically applicable to the manufacture of positive nickel electrodes chemical pretreatment of a suitable, electrochemically active nickel mass.

So far, only one nickel-II-hydroxide process is known in this field by ozone in a suitable reaction medium as powder (D8P 1 240 056 and DBP 2 122 165) to oxidize to higher quality nickel oxide hydrates. Recently it is about this a way of the company Westinghouse (US.Pat. 4,481,128) became known, in which the whole with Ni (OH) 2 made positive electrode is subjected to an ozone treatment.

Not known and so far have failed are all metallic attempts Nickel powder in an electrochemical way in a chemical way that is easy for battery production to transfer active nickel oxide. The method according to the invention uses against it a nickel powder that has not yet been for this purpose into consideration has been drawn, namely amorphous, non-magnetic, by reduction from nickel salt solutions Nickel powder obtained with boranates. This nickel powder can be used in addition to electrochemical Way also in a surprising way directly through gaseous ozone in alkaline solution convert to higher-quality nickel oxides, which are precharged plus mass in alkaline Accumulators can be used.

In the process, the amorphous, non-magnetic, very fine and separately produced nickel powder is slurried in an aqueous-alkaline solution of alkali hydroxides, preferably a potassium hydroxide solution with an addition of 5% LiOH, and ozone is introduced. It is important to ensure that the reaction components are mixed as well as possible. With a suitable set-up of equipment, 100% conversion of the ozone is possible. The reaction equation follows the general equation: respectively The pH of the reaction slurry should be greater than 8. The deep black reaction product obtained by the ozone can be easily filtered and, apart from the boron inevitably present from the boranate reaction, does not contain any foreign anions. Some of the boron is also oxidized out of the mass and goes into the liquid phase to be filtered off. Otherwise, boron is irrelevant for the functionality of the alkaline accumulator.

The inventive method leads to an electrochemically active, higher quality nickel oxide, mixed with the usual conductive additives, directly to the Pocket or tube electrode production can be used. The high reactivity of the amorphous nickel also allows an almost 100% conversion of the starting material.

Exemplary embodiment: In 500 ml of a 20% potassium hydroxide solution with an additive of 2% LiOH 50 g of the very fine, amorphous and non-magnetic nickel powder registered. A stirring or vibration system ensures thorough mixing of the slurry. Now the ozone gas stream obtained from an ozonizer (about 2% ozone in air) passed through the slurry in an amount of 50 liters per hour. The reaction runs at room temperature. The reaction has ended after 36 hours.

With a gas stream more concentrated in ozone, the conversion proceeds accordingly more quickly. The end product that does not differ in color from the original product is filtered off, washed and dried at 800 ° C. in a vacuum drying cabinet. To Determination of the oxidation equivalent, the so oxidized mass comes from higher valued Nickel oxides directly for processing in dry pre-charged pocket or tube electrodes for alkaline batteries.

Claims (3)

Claims: 1) Process for the production of higher quality nickel oxides for electrical accumulators by chemical means, characterized in that by Reducing boranates, preferably alkali or ammonium boranates, from nickel salt solutions Obtained, amorphous and non-magnetic nickel powder in an aqueous-alkaline Slurry is oxidized directly by a stream of ozone gas. 2) Method according to claim 1, characterized in that the alkaline, aqueous reaction medium consists of a solution of the alkali metal hydroxides and has a pH greater than 8 is present. 3) Method according to claim 1 and 2, characterized in that the Reaction slurry by stirring or vibratory mixing in an intimate contact with the ozone gas is held.