DE1496192A1 - Rechargeable power generating cell and electrode therefor - Google Patents

Description

OlPIL.-ΪΝβ. H. SOKlFFER 'ί4Β6ΐν2

Patent attorney ■ K arfsru he / Baden

Patent application (9371}

ill-iiDj G-atwicit

Sussex, England

'wiecLerauzladbara Stromzeugeiade cell and electrode therefor

The invention relates to a sisramerzeugende ^ wiederauxlacLtoare 2elle and for "particularly suitable Slefctrode _o Bie Erfindwig" is based on the finding that _f Titaniujn Weyen its low "* Wiclite its
cheaiisclien passivity and its polarizing
3i _; ? make an excellent CrsLger for a coating of Ilanganedioxide. "which forms through the. disintegration of a" Manfjan compound which is unstable at higher temperatures "is a suitable manganese compound
is, for example, hangan nitrate, which when heated
on about 25o ° G in manganese dioxide and step-solids dioxide. disintegrates. ■ ■ ■ ■ ■ ■ ■

A aoleher "by a pyrolytic process generated uborzug of manganese dioxide is a auss he neatly fes-t ^ nae Ivrxtt bond with the titanium Iraqis a ·. IN THE
xi-i> :. iriiura 7 / ir "KungüToll for a porous cathode
ψ * ζχ. ' // can end so that it can be impregnated through and through with an active pepolarizer.

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must, 'the porous body made of titanium impregnated with icangan nitrate' .verden, which in the. pyrolytic process with the. Titanium reacts and thereby forms a non-polarizing coating that is directly connected to the surface of the pores , without the connection between the individual pores and the

to destroy these pores "

The chemical that takes place at the pyrolytiaeheu process The reaction can be represented as fol. ';; t ί

Mn (SO.,} Ρ ■ ¥ heat ■ - ♦ * IvSaOp + 2BOp.

The Mitratradifcal · released in the process is obviously responsible for the fact that in this way a nicatpoiarizing MnOp. - Coating occurs in the complete absence of a polarizing titanium _{oxide film between the titanium support and the EnG 0 coating.} This iüt of crucial importance for rechargeable cells _t in which the reversible properties of Ilan in Israel ^ ancüoxyds exploited ', -' Ground * For if einije make the wearer from Titanium. because of the unavoidable imperfections of the iian-jandioxydüberzUiyes initially remained open », then wüx'deii

these "put in place with a polarizing layer Titaniumoxj'd overlay and so these would be practical isolated from the electrolyte »The fact *

that in the pyroiytic process aur-JßrKei ^ imij; of

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iuangandioxyd coating no titanium oxide film arise. " can, results in better efficiency during the charging process, Because the charging current is only directed to the triangular oxide coating, which causes the cooling of free oxygen and the waste of charging current on the ■ inactive parts of the surface is prevented *

The highly effective cathode according to the invention, the axis Eitenium and a pyrolytically applied, adherent "coating consists of manganese dioxide in connection with a zinc or kaämium anode and an alkaline electrolyte such as a white solution of potassium hydroxide, an extraordinary one good, rechargeable cell »

In 13s, however, it was found that a: porous titanium cathode, in which the surfaces of the pores are also provided with a pyrolytically produced manganese dioxide coating, in combination with a zinc anode and an acidic zinc salt "electrolyte, a rechargeable" electrolyte A cell that is noοh better than a rope with the same electrodes - but with an alkaline iilektroljten as well as an acid electrolyte that contains tin ions, such as zinc sulfate, can withstand a significantly larger number of charges and discharges without interference than cells in which

trolyt 7erwendun _f v; finds.

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Another advantage that the acidic electrolyte has itself "brings" consists in that while charging the zinc deposits without dendrite formation and without internal short circuits caused by alkaline or oxidic zinc compounds are caused

Further advantages of the present invention emerge from the following description in conjunction with the accompanying one Drawing, the single figure of which represents a longitudinal section through a rechargeable cell according to the invention "

In the manufacture of a preferred embodiment of the invention, a porous titanium plate is thereby obtained manufactured by filling litanium powder into a 1.6 mm deep cavity in a graphite block. afterwards the excess powder is stripped off and then the block with the titanium powder in a vacuum oven up to the sintering temperature between 119o ° C and 1275 ° C is heated, the heating time being about 3o minutes at 125o 0 and correspondingly longer at lower sintering temperatures. Of course, the depth of the cavity in the graphite block can be adjusted accordingly the desired thickness of the titanium plate to be produced to be changed. The process described results without any compression of the litanium powder a firm before the sintering process coherent, unified body that is

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characterized by uniformly distributed and interconnected pores, the porosity being in the order of iron 60 fo .

the sintering Eitaniumbleanstreifen be ung spot welding-connected to the porous 2itaniumplatte through, then with an aqueous solution of manganese nitrate having a concentration of 2o bis-5o $>, preferably 5o f * _t is impregnated. The impregnated plate is then heated to 25o G until all of the material is eliminated and a tough coating of manganese dioxide is achieved that adheres to the entire inner and outer surface of the porous titanium body. This organ is repeated until the maximum possible amount of manganese dioxide is deposited everywhere in the porous iEitanium mass without the interconnected pores of the litanium body being clogged.

The optimal grain size distribution can be found in the practical Execution through a sieve analysis of the titanium powder used be determined.

The "so far - Mt.". Of the powder was a practical implementation, at 21, ⁿ Scott Apparent Density "v / ar 22.9 g / om The pressure in Yafcaum furnace during sintering tervorganges O oj was in the order of 0.4 microns down to 0.06 microns during the time the sitanium powder is

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was heated to the sintering temperature.

Although the method described, in which a compaction of the titanium powder was avoided before the sintering process, which ensures the greatest possible porosity, Of course, a porous litanium plate can be made according to the conventional methods, where the litanium powder is pressed before sintering ο In this case-- the porosity can be added by adding a volatile binder to the powder, such as an alkyd resin, which can be enlarged without leaving a carbonaceous residue evaporated

As previously stated, a porous sintered S & nium plate is the preferred support for the fabrication a cathode according to the invention. Of course you can If necessary, reinforce the strength of such a plate by adding titanium powder on a! Ditanium wire mesh that piles formed for example from 0.15 mm thick titanium wires is.

! The titanium powder on the QJitanium fabric will then

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sintered in a vacuum in the "already" described manner « In addition to its function as a mechanical reinforcement, the litanium tissue can also act as a conductive Connection lugs are used. It is also possible through the described pyrolytic process from a manganese nitrate solution directly on a dense litanium göwebe or on a thin, knock down non-porous litanium sheet Though the capacity of the cathodes, which in the manner described is directly due to the precipitation of MnOp litanium fabric or! eitanium sheet can be formed, is limited, such cathodes can be used for special Applications to be very two-dimensional «

In the accompanying drawing is denoted by the reference number denotes the cathode, which consists of an elongated, porous titanium plate and has been produced as already described above. The with each other connected pores of this plate are covered with a pyrolytic coating of manganese dioxide overdrawn. This plate is as porous as it can possibly be and as far as the mechanics can see strength of this plate for the intended use. In a practical example this plate had a porosity of about $ 60. The anode is according to the illustrated embodiment formed by a pair of elongated zinc plates 12 previously priced at $ 2 to $ 15, preferably Io #, (percent by weight) mercury ^ algamxert -S-

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have been.

A barrier layer 14 is between the cathode Io and the anodes 12 are turned on and can be made of fiberglass or made of a porous plastic, such as "Synpor" (with inikrof a pore-provided Polyvinyl chloride) or made of "Polypor" (nylon- " tissue that has a microporous Plastic is laminated) exist. This spacer layer must be ion-permeable, but the passage prevent products from developing on the electrodes

The electrodes are mounted in a container 16, which consists of a suitable plastic, such as polyethylene, the upper end through a cover plate 18 made of a similar material is tightly closed.

The plate-shaped titanium electrode Io is on her upper end with one titanium strip each on both sides connected by spot welding. These sheet metal strips are attached to the cover plate 18 by means of a screw bolt 22, which is through holes in the Sheet metal strips and the Deokplatte passes through and is provided with nuts 24 and thus the externally accessible Cathode connection of the cell forms

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"Preferably, the iitaniumblechstreifen 2o with the porous litäniumplatte Io be connected by spot welding, before it is provided with Sitaniumplatte pyrolytically deposited manganese dioxide _y thus a good sulfur bonding can occur.

The anode plates 12 are bent upwards so that the ends ⁵ of the anode plates 26 is about extend horizontally. Through holes arranged in these ends 26 and thus aligned holes in the cover plate 18, screws 28 are passed, which together with the associated nuts 3 o form the anode connections accessible from the outside.

In most cases, the two anodes 12 are connected to one another, which is inside the oiler outside the cell can happen, which is a matter of course for any expert in this field represents * The ropes inside the cell the bolts 28 are coated with an epoxy resin to protect them from chemical attack «

The container 16 is filled with a suitable acidic ülektrolyten 52 filled so far that the electrodes completely immerse in this electrolyte, the Electrolyte is an aqueous solution of «Inksulfat (ZnSO ^ 'γ H ^ o), uie by dissolving Io biu öo Ge-7 / icht per cent, preferably 50 percent by weight

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₄ * 7.H ₂ O is obtained in 100 ml of water «. The electrolyte preferably has a ρττ value of about 4.5.

A valve 34, which responds to excess pressure, is built into the cover plate 18 and comes into operation if the internal pressure in the cell exceeds a certain level, in order to prevent any oases that may develop in the interior of the container. outdoors, to lead that for too long. Charging of the cell or the presence of contaminants aar electrodes, the electrolyte and the container. Since this. Pressure relief valve can be designed in a known manner xmL · not. A detailed description of this valve and its mode of operation can be dispensed with here. .. -

In the current drain from the cell of the coating of f -Mangandioxyd (MAOP) is reduced to iki.Jd ^ ~ w && the zinc of the plate-like anodes 12 are ionized and dissolved as zinc sulfate · "

During the charging process, metallic zinc is deposited again on the anodes and the HhpÖ ^ is oxidized to IvJhO ₂ (Ma ₂ O ₅ + 0 P =? Z- MnO ₂ ) ■ «

The resistance coefficient of the electrolyte is very low, and it is also between the electrodes of the Cell an ion-permeable barrier layer 14 is provided the local agglomeration of precipitation or the nie

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to prevent unwanted particles from hitting the anode. The potential of the cell depends in a "way" on the load current Lich 1.77 YoIt ", so that with a cure ζ final span With a voltage of 1.0 volts, an average voltage of 1.3 volts can be achieved is.

Bs vrarde also found that an admixture of aluminum sulphate (Alp (SO.) ^ To the electrolyte is two-dimensional and advantageous, because this admixture contributes to the fact that the intended Jj ^ value can be maintained within narrower limits » ^;

Aluminum sulfate also serves as an additional active ingredient and also as a buffer substance through the formation of colloidal aluminum metahydroxide AlO (OH) if the Pjj value rises above the value 4. The addition of aluminum sulfate to the electrolyte also favors the Even, dendrite-free zinc precipitation on the anode during the charging process.

The amount of buffer substance (aluminum sulfate) can be in the order of magnitude of 1.5 to 3 grams / Ioο ml of the electrolyte (zinc sulfate).

Of course, other buffer substances such as the Acetates of the alkali metals, for example sodium acetate, magnesium or ammonium sulfate e. Find use «,

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The above is a "preferred exemplary embodiment inventive cathode, the coating of a by one pyrolytic process created hangan dioxide layer on the inner and outer surface of a porous fitanium electrode has been described. However, it has been found that lead nitrate can also be used to remove the porous sita-

iaLt nium electrode to be impregnated. When the lead nitrate Pb (ϊΓΟ ^) ρ impregnated titanium plate is heated to 51o ° 0, the lead nitrate decomposes into lead monoxide (PbO), nitrogen peroxide (2 HO ₂ ) and oxygen (1/2 O ₂ ), whereby the Lead monoxide precipitates as an adherent and tough coating on the surface of the porous litanium electrode. This lead monoxide precipitate can then easily be transformed into a lead dioxide coating (PbO ₂ ). The cathode made of titanium and a coating of PbO ₂ , with a zinc anode and a zinc sulfate electrolyte, also makes a very useful rechargeable cell.

Zinc sulphate (ZnSO, * 7H ₂ O) has been designated as the preferred electrolyte, but electrolytes other than zinc sulphate can also be used, such as those which contain zinc ions and in which the hydrolysis of the zinc salts is a value below generated by 7, ο, such as zinc acetate, zinc sulfamate and zinc nitrate.

As with all acid electrolytes, it is also in this one. Case of essential importance that the zinc anode is, so that local reactions are prevented.

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Obviously, the invention is not based the above-described electrodermic materials and the above-described electrolytes "limited, within the scope of the concept of the invention - by the person skilled in the art without further ado by other materials or Orders are replaceable "

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Claims (1)

21 «September 1964- '■' (9371) Claims 1. Electrode.for electricity-generating, rechargeable cells, '. ■ -.' ■ - - -, - ■ --_ marked with ».. - .-- ·. ■. ■, ■ that the electrode is made of titanium and that its surface is provided with an adherent, pyrolytically produced coating of a metal oxide. 2 »Electrode according to claim 1, characterized in that the pyrolytically produced coating consists of a metal oxide of manganese dioxide or of lead oxide ^; consists. 3. The electrode of claim 1, characterized in ^{1 '-;} is generated that the coating and its adherent connection with the! Eitanium electrode by wetting the surface of the electrode ¹ with Mangahnitrat and its Erhitzmig to the decomposition temperature of the manganese nitrate. ' ^:: 4. Electrode according to claim 1, characterized in that the titanium electrode consists of sintered titanium powder and has pores connected to one another, and that the coating of mahogany dioxide is firmly adhered to the inner surface of these pores, in which the porous titanium electrode is reacted with a manganese compound ^v in closest Kontajct and then brought to a temperature which decomposes the manganese compound in which. . '";' 9 09 813/1159 (9371) ^ 5. "rechargeable cell, characterized in that that the cathode consists of .sintered litanium powder and having intercommunicating cavities, being the entire inner and outer surface the porous cathode with a firmly adhering pyrolytic generated coating of a metal oxide, e.g. from hangand dioxide or lead oxide is provided that the anode is made of It consists of cadmium or zinc and that with cathode and iknode an electrolyte is in contact. 6. A rechargeable cell according to claim 5, characterized in that that the electrolyte is essentially out an alkali metal hydroxide ». 7 β rechargeable cell according to claim 5, characterized characterized in that the electrolyte is a hydrolyzable acid salt that is in contact with the cathode and anode the rhythm is on. 8. Rechargeable cell according to claim 5 »thereby characterized in that the electrolyte is an acidic, aqueous solution containing zinc ions, the electrolyte of zinc sulfate, zinc acetate, zinc sulfamate and / or Zinc nitrate can exist, ■ ... y ₀ v / ieder chargeable cell according to claim 5 »characterized in that the electrolyte consists of an aqueous Solution of zinc sulfate consists that the negative electrode 9098 13/1159 '■ U96192 (9371) century _ is made of amalgamated zinc and that the positive electrode consists of a porous body made of sintered Titanium powder consists of sere. and. inner Surface with an adherent coating of · manganese dioxide is stranding that through. Soaking the porous öhLtaniUBi electrode with manganese nitrate and. subsequent Heating ids to decompose the manganese nitrate is, and that an ion-permeable barrier layer between the positive and negative electrodes is arranged. ■ Io. Four chargeable cell according to claim 5, characterized in that an electrolyte consisting of Iq to 80 "parts by weight of ZnSO-" 7 H ₉ O, dissolved in 100 parts by weight of Yifasser, is provided within a container, as well as a negative electrode made of amalgamated zinc with 2 to 15 percent by weight of mercury, which is immersed in the electrolyte, and a positive electrode made of a porous titanium body with a firmly adhering coating of manganese dioxide on the entire outer and inner pore surface, this coating by heating manganese nitrate during contact with the surface of the titanium -Electrode up to the decomposition temperature of the manganese nitrate · is achieved. 11. A rechargeable cell, characterized by two electrodes and an acidic electrolyte, one of which _; the electrodes made of amalgamated zinc, the other made of one 3 0 9013/1159 1498192 |> orosen ilitaniumorper toestehti. the nit buckets "■ pyrolytically he generating toil f MTFA & it & mM®. Üfeerzuf au® Lea & gandiiöxyd stranded 1st Wöfeei äuöii the inner surface of -Boren the fitsuaium-llektroCe having this Überziiig ,, UIID Dall def 'llektäTQijt from EIA & r aqueous Löätmg from Einksulfat fees splits lä & d a foot * - removes * ■ -: ,, 12 · Rechargeable cell according to claim 9, characterized by the fact that the buffer station from 1 _>; 5 to-is ^ 3 Sraöim Aluaiiniumisulfat Je Ioο ml des -Elei-trölyten bestent * · 13 * Again aflädfeäre cell after Jnspruck Ιό, dä & urch marked that the iüffersütoatanz a connection or alkali metal acetates, magnesium sulfamates . and / or Amoniumsülfamaten is * 14ο process for preparing a "electrode for again aüfladiDare cells, characterized in that a porous ÜJitaniumplatte is pregnated with manganese nitrate in the ^ _# that the plate then feia zua ZersetzühgBtemperatur of said manganese nitrate is heated WOT) ei a firmly adhered on the ^surface:? Tough ^ Coating made of manganese dioxide on the entire surface einaohlieeslieii iier dea: pores are formed » camouflages H9S192 15. Procedure me lerstellyj &f; a duct £ re-detachable! skins »€ 'that öia austitaaiuffipulr ^ r through iisi% © im iEbodöi · with lajiiijeirBiJiiaiaA © ^ ia aiit a Üösuftg t oa Mäüga & ftitarnt on a ffeaperalmr of about tgo ⁰ Ö to MäJAxmg on the total & fi OibeffläGlie fSBÄafteMei ijh & zziigen from laafaiidiöiiqfd e3 ± i.ts; i; wi £ -d uM that the process of impräiäieiis üad des a & se3ali «ssäeftd% & Mtzeiis meHrfaöii is re-oiled * until - © ine thick MaSigaadiox ^ duTDersiUgssoliiciit in desa Porea is" tasa afe $ r the connection between the individual rooms is preserved 1 € »YerfaiLren for the preparation of a shelter for AktaMU>« latören »characterized in that the titanium Existing electrode lead was sprayed on and then the Electrode heated up to the decomposition temperature of the element being »taking a on the surface of the fitanium electrode firmly adhering and tough film of lead oxide is formed » 9Ö9Ö1i3 / H-S-9