IMPROVEMENTS IN SECONDARY VOLTAIC BATTERIES
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by August Partz at the Office of the
Commissioners of Patents on the 9th May 1883.
AUGUST PARTZ, of N° 9 Christchurch Road, Hampstead, in the County of
Middlesex, "IMPROVEMENTS IN SECONDARY VOLTAIC BATTERIES"
This invention pertains to that class of secondary voltaic batteries or so-called
electric accumulators the action of which is based on an alternate peroxidation and
disoxidation of a metal..
Apparatus of this kind have generally been made with electrodes of sheet lead,
and between these fibrous material has been interposed to keep them separate and
a coating of oxidized or spongy lead attached to them. Such electrodes have been
found to be subject to disintegration because of the gradual inroad made by the
chemical changes produced upon them, and the substances that could in other
respects fitly be used for permeable partitions or envelopes have been found not to.
withstand the destructive effect of dilute sulphuric acid
The first part of my invention relates to an electrode which will not become
disintegrated and does not require to be protected by a cover of woven or felted
material. The electrode is composed of carbon and lead in such a way that the
latter is embodied or encased in the former so as to be secured against becoming
detached, without being rendered inacessible to the electrolyte. The carbon must.
be porous, or perforated, or both, and is accordingly either impregnated or otherwise
intimately combined with oxidized or finely divided lead, or its perforations are
filled therewith, while to the same purpose two permanently united plates of such
carbon may be made to enclose a layer of such lead
Carbons which are to be impregnated with lead should be as porous as they can
be made without becoming too friable or too deficient in their capacity for electric
conduction. They are most suitably employed in the shape of plates about half an
inch thick.. To impregnate such carbons. I soak them from five to ten minutes
in a boiling saturated solution of acetate or nitrate, or infused chloride of lead,
and then cause the absorbed salt to be reduced, or to be converted into oxide, by
chemical or by electric action. Preferably I soak them in fused chloride of lead
heated to redness, and then connect them with anodes of carbon in a solution of
sodic or potassic hydrate or carbonate and effect the reduction of the chloride by
an electric current.

page_text: Electrodes similar to those of impregnated porous carbon may be obtained by
subjecting a mixture of about equal parts by weight of powdered carbon and
minium to which a solution of a small percentage of shellac has been added, to
hydraulic pressure and then the agglomerated | lates or slabs to a heat just sufficient
to melt the lac.
Perforated carbons are not necessarily, but most advantageously made of more
or less porous material. When single plates of them are used for electrodes, the
holes in them should be from an eighth to three sixteenths of an inch wide and as
close together as is consistent with the requisite solidity of the plates. They may be
filled either with minium or with spongy lead precipitated by zinc from an acetate
solution.
As carbon plates which shall hold a layer of a preparation of lead between
them must be comparatively thin, and as such plates of the dimensions usually
required cannot well be made very porous, it is generally best to have them also
perforated, but in this case the holes need not be wider than a sixteenth of an inch.
To make an electrode of two such plates, they are so joined to a frame placed
between them as to form therewith a narrow receptacle which is filled with minium
or spongy lead.
_Electrodes composed of carbon and lead in either of the above said ways and
forms may be employed in the same well known manner as electrodes of lead
plates, excepting that they are not to be covered with any fibrous substance. To
fit them for being placed in electric communication, I rivet to them along their
upper edges strips of lead with projecting ends to which pole wires or other
conductors may be attached.
In secondary batteries in which the active conditions of both, the positive and
negative electrodes are restored through chemical changes produced on lead by the
primary current, the kathodes preserve much of their potency after the anodes
have ceased adequately to co-operate. This is owing in some degree to a partial
conversion of a layer of spongy lead upon the anodes into sulphate by local
action, 'but must principally be attributed to the difference between the effect of
the actual fixation of the oxygen during the process of charging, and that of the
retention of the hydrogen by mere occlusion in a layer of spongy metal.
The second part of my invention is intended to render the strength and con-
tinuance of secondary currents independent of changes in the state of the anodes.
It consists in the combination with an electrode made substantially as and in either
of the forms herein above described, when used as a kathode of an anode of
amalgamated zinc, that is to say of a metal which dissolves in the electrolyte and
the potential of which therefore remains constant.
When a secondary voltaic battery made on this plan and containing dilute
sulphuric acid is first charged by a primary electric current, lead is peroxidated
and bydrogen is disengaged upon the anodes; when it is discharged, peroxide of
lead is reduced and an equivalent of zinc is oxidated and dissolved; when it is
re-charged, lead is reperoxidated and the dissolved zinc is restored to the anodes.
To avoid the care which is to be bestowed on anodes of zinc with reference to
their amalgamation, they may be replaced by anodes of copper in cases which
do not require the employment for the purpose in view of the smallest number of
elements.