DE2206002A1 - Alkali accumulator anode - contg metal complex to improve utilisation of active oxidising cpd compsn - Google Patents

Abstract

Anode comprises active compsn. of oxidising cpds. of Ni, Co or Ag intercalated in a metallic structure or a porous metal carrier, compsn. contains 0.01-6 pref. 0.1-2 wt % complex of formula: (where A forms an opt. substd. aromatic or heterocyclic ring, R1 and R2 are 1-4C alkyl or H, M is Mn, Fe or Co).

Description

Our reference: O.Z. 27 967 Ki / Be anodes for alkaline batteries Anodes for accumulators with alkaline electrolytes consist of an electric conductive, electrochemically inactive metal framework, in whose pores the active mass, for example, nickel oxide hydrate, cobalt hydroxide or silver oxide is incorporated. Instead of the metallic framework, porous metal pockets, such as those made by the Edison accumulators are known to be used. The active mass will be here, to ensure sufficient electrical conductivity, metal flakes or grains or graphite added. The disadvantage of both types of electrodes is that on the one hand the active mass can only be used to 80 to 85%, on the other hand, that it comes to the evolution of oxygen before the end of the charge. By this unwanted oxygen development, which depending on the type of electrode can be up to 50 % Of the charge loss results, it is necessary to remove the cathode in the case of gas-tight accumulators oversized in order to bind the oxygen formed. These measures worsen but, especially compared to the lead-acid battery, the power-to-weight ratio is decisive.

It has now been found that the active mass of anodes for alkaline accumulators, consisting essentially of active mass of oxidic compounds of nickel, cobalt or silver stored in a metallic framework or in porous metal pockets, can be better utilized if the active masses are 0 , 01 to 6% by weight of metal complexes of the general formula contain, in which A denotes an optionally substituted divalent radical which completes the part of the molecule -C = C- to form an aromatic or heterocyclic ring, the radical R1 as well as the radical R2 represent a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms and Me means manganese, iron or cobalt.

Complexes of the above formula are for example: Particularly favorable results are achieved with complexes with cobalt as the central atom. The radical A is preferably the addition to a benzene ring. The production of complexes of the formula I is the subject of the patent. ... ... (patent application P 15 69 667.0-43).

The metal complexes can be mixed and mixed into the active mass subsequent introduction into the supporting framework or metal pockets. But it is also possible to impregnate these complexes afterwards to bring in otherwise finished electrode. The impregnation can be with solutions or Suspensions of the metal complexes in a suitable solvent, e.g. N-methylpyrrolidone or pyridine. After impregnation, the electrodes are dried, expedient at temperatures below 1600C, especially below 100ob in the air stream, to avoid sublimation and decomposition of the metal complexes.

The metal complexes can, however, also be oxidative before they are introduced Are subjected to treatment, for example, that they are in Acids, such as concentrated sulfuric or phosphoric acid, dissolve and the effect exposure to oxidizing agents, such as nitric acid, but especially oxygen or oxygen-containing gases, such as air, The treatment can take place at room temperature or elevated temperatures up to about 1000C can be carried out.

In addition to the metal complexes, the active material can also be organic and / or inorganic ion exchangers and those mentioned above, the conductivity increasing substances are added. Suitable organic ion exchangers are those based on copolymers of styrene or styrene derivatives, which are used as charge-carrying Groups contain, for example, sulfo groups or quaternary ammonium groups, preferably so-called gel exchangers without macropores can be used, while as inorganic ones Exchangers permutites and oxidic compounds of zirconium come into consideration. The content of the ion exchangers in the active material can be 0.1 to 2.0% by weight.

Example 1 A mixture consisting of 40 parts by weight of fine-grained Nickel hydroxide with 6% by weight of cobalt hydroxide, 59 parts by weight of nickel granules with a grain size of 80 / u and 1 part by weight of sublimed cobalt complex of 5,14-dihydro-dibenzo- E 1-05,9, t4,1i -tetraaza- E4 -annulens is applied at room temperature using a Pressure of 12 t / cm2 to a cylindrical shaped body of 15 mm diameter and pressed to a thickness of 1.6 mm. The shaped body is covered with a nickel mesh taken, the wire thickness is 0.13 mm and has 800 meshes per cm. the The finished electrode is immersed in 25 percent by weight aqueous potassium hydroxide solution for 2 days. After 13 charging cycles with a charging or discharging current of 50 mA, the electrode is formed. After 14 charging cycles, a capacity of 310 mAh / g active mass is achieved or 123.5 mAh / g electrode without mesh. Comparatively, an electrode provides that contains no metal chelate and a total of 41 wt. nickel hydroxide with 6 wt. cobalt hydroxide contains, after their formation, a capacity of 210 mAh / g active mass, or

84.0 mAh / g electrode without mesh.

Example 2 A porous sintered nickel plate with dimensions of 70 mm x 25 mm x 0.8 mm, which contains 1.28 g of nickel hydroxide, is saturated with a Solution of the cobalt complex of 5,14-dihydro-dibenzobenz F5,9,14,18 # -tetraaza- L ## - annuiens impregnated in N-methyl-pyrrolidone and then for 24 hours dried at 150 ° C. The cobalt complex is previously in 96 percent strength by weight sulfuric acid dissolved (20 g / l) and treated oxidatively while passing air through. By the exothermic reaction increases the temperature to about 50 ° C.

The treatment is over after 3-5 hours. The one who fails Solid was separated from the sulfuric acid, dried and dissolved in N-methylpyrrolidone solved. The finished electrode is immersed in 25 percent by weight aqueous for 2 days Immersed in potassium hydroxide. Achieved after forming the electrode through 12 charge cycles one has a capacity of 333 mAh / g active mass at a charging current of 100 mA. In comparison, the same non-impregnated electrode has a capacitance of 252 mAh / g active mass.

Example 3 A mixture consisting of 62.2 parts by weight of silver oxide, 1 part by weight of the cobalt complex of 5,14-dihydro-dibenzo- [b, ij -F5,9,14,18] -tetraaza- L14l-annulens and 36.8 parts by weight of nickel granules with a grain size of 80 / u increases at 2 room temperature using a pressure of 12 t / cm2 pressed into a cylindrical molding of 20 mm in diameter and 6.9 mm in thickness. The shaped body is made with a nickel mesh of 0.13 mm wire thickness and 800 mesh edged per cm2. The finished electrode is in 25 percent by weight for 2 days Immersed in potassium hydroxide. After formation through B charges and discharging, the electrode has a capacity of 236 mAh / g active mass, resp. 147.0 mAh / g electrode without mesh. In comparison, an electrode of the same type provides without the metal complex a capacity of 226 mAh / g active mass or 140.2 mAh / g Electrode without mesh.

Claims (4)

Claims 1. Anodes for alkaline accumulators, consisting essentially of active material embedded in a metallic framework or in porous metal pockets made of oxidic compounds of nickel, cobalt or silver, characterized in that the active materials are 0.01 to 6% by weight of metal complexes of the general formula contain, in which A denotes an optionally substituted divalent radical which completes the part of the molecule -C = C- to form an aromatic or heterocyclic ring, the radical R1 as well as the radical R2 represent a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms and Me manganese, iron or cobalt means0 2. Anodes according to claim 1, characterized in that the active masses metal complexes in an amount of 0.1 to 2 percent by weight included. 3. Anodes according to claims 1 and 2, characterized in that! 5 the active masses contain metal complexes of cobalt. 4. Anodes according to Claims 1 to 3, characterized in that the Metal complex of the cobalt complex of 5,14-dihydrodibenzo-Lb,) 9s14s18l-tetraaza- E4 is -annulens.