provements in the Manufacture or Production of Electrodes for Secondary Batteries.
Year: 1898

page_text: Date of Application, 12th Jan., 1898
Complete Specification Left, 12th Oct., 1898-Accepted, 12th Nov., 1898
PROVISIONAL SPECIFICATION
Improvements in the Manufacture or Production of Electrodes for
Secondary Batteries.
I, CHARLES POLLAK, of 253, Mainzer Landstrasse, Frankfort-on-the-Main, in
the German Empire, Managing Director of "Accumulatoren-Werke System
Pollak," do hereby declare the nature of this invention to be as follows:-
It has hitherto been assumed that in the electrolysis of solutions containing
lead, or of any electrolyte placed between lead plates, lead peroxide is invariably
obtained at the anode. I have ascertained however that under certain conditions
the result may be lead at lower stages or degrees of oxidation while at the same
time its salts may form in the electrolytical process provided a predetermined
"critical" voltage consistent with the nature of the compounds alluded to is not
exceeded. In the case of lead electrodes at 1 volt constant electromotive force the
resulting products will be sub-oxides of lead of a grey colour and other lead salts
poor in oxygen; at from 15 to 18 volts there will be obtained orange-red lead-
oxides very nearly approaching red lead; while at an electro motive force of over
2 volts the well known peroxide of lead will form. In order to attain these results
the electro motive force of the electrolytical cell should in no case exceed what,
in regard to the given body, may be described as the critical, point. The insertion
of resistances with a view to destroying part of the electro motive force does not
lead to any satisfactory results save in those cases where electrolytes are employed,
in connection with which a local action arises at the electrodes, and where operations
are conducted with a very small amount of current. This may be accounted for
by the fact that the local action under those circumstances acts more rapidly than
the weak current. Thus where the amount of current is exceptionally slight, for
example, a layer of lead sulphate may be obtained in dilute sulphuric acid upon
the lead anode. But where it is proposed to operate with comparatively large
amounts of current care should be taken to see that the source of current exhibits
precisely the requisite voltage or that such voltage is secured by the interposition
of counter electro-motive force in the form say of polarizers or accumulators. The
internal resistance of the cells thus interposed, and of the source of current and
conductors, should be as low as possible so as not to influence the amount of
current in an appreciable degree. Where more electro motive force is available
a number of electrolytical cells may be connected in series care being taken that
all the cells are as nearly as practicable alike, failing which totally different pro-
ducts might be obtained in the several cells. Let it be assumed for example that
in a number of cells with lead electrodes the surface, or area, of the anodes is
considerably less than in the remaining cells; the consequence will be that on
these smaller anodes lead peroxide will form instead of lead at the desired lower
grades of oxidation; and similar alterations must be occasioned by other
variations such for example as in temperature density of the electrolyte and the
like.
In lead plates of the Planté formation the difficulty has invariably been observed

page_text: that in a short time the positive plates became covered with a thin, though dense,
film of peroxide of lead whereby the electrolyte is precluded from any further
action nenetrating the plates so that it takes a very long period to complete the
electrode formation by that method. It was necessary also to reverse the current
at frequent intervals that is to say to effect a series of oxidations and reductions
in order to obtain a sufficiently deep layer of peroxide upon the plate.
By my process electrode plates to be formed can in a very short time be covered
with a deep layer of oxide by the electrolytical process.
"
According to this process the cells should be connected to a source of current
of a maximum electro motive force of 2 volts. One storage cell will therefore
prove a sufficient source of electricity for one formation cell or for two such
cells connected in series. The cells are subjected to the action of current for a
greater or lesser time according as a thin or thick layer of oxide is to be obtained
on the plate. After the lapse of the time allowed the plates will be found to be
covered with a perfectly firm and cohesive, though porous, layer of oxide of lead.
To accelerate the action it is advisable to raise the temperature of the cell being
formed to about 40 degrees centigrade. This mode of treatment of the plates 18
not however to be regarded as formation proper but as a preparatory operation
or the initial stage of the formation process.
The plates covered with lead-oxide by this method may now be converted into
either negative or positive accumulator plates by further electrolytical treatment
by any well known process. "To enable the plates to be used as negative electrodes
all that is required is a subsequent reduction, say, in dilute sulphuric acid, while
where positive accumulator plates are to be formed the plates should either be
peroxydized directly or first reduced-as in the case of the negative plates-and
then peroxydized. In this process of treatment the whole of the preparatory layer
of oxide becomes converted into peroxide in a concrete form so that excellent
positive electrodes are obtained as a result.
This process is an outcome of the observation that in electrolytical cells the
nature of the chemical compounds depends upon the voltage of the electro motive
force while the quantity of chemicals produced in the course of the operation in
accordance with the well known law continues proportional to the amount of
current.
A further feature of this process is that in its performance the lead-oxide is not
precipitated upon the electrodes from lead salts but by the oxidation of the metal
of the electrode itself, it being immaterial what other electrolyte is used.
Dated this 12th day of January 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture or Production of Electrodes for
Secondary Batteries.
I, CHARLES POLLAK, of 253, Mainzer Landstrasse, Frankfort-on-the-Main, in
the German Empire, Managing Director of "Accumulatoren-Werke System
Pollak," do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
•
;
It has hitherto been assumed that, in the electrolysis of solutions containing
lead, or of any electrolyte placed between lead plates, lead peroxide is invariably

page_text: obtained at the anode. I have ascertained however that, under certain conditions,
the result may be lead oxides or salts at lower stages, or degrees, of oxidation,
provided a pre-determined "critical" voltage, consistent with the nature of the
compounds alluded to, is not exceeded. In the case of lead electrodes at 1 volt
constant electro-motive force the resulting products will be sub-oxides of lead of a
grey colour and other lead salts poor in oxygen; at from 15 to 1'S volts there will
be obtained orange-red lead oxides, while at an electro-motive force of over 2 volts
the well known peroxide of lead will form. In order to attain these results the
electro-motive force of the electrolytical cell should in no case exceed what, in
regard to the given body, may be described as the critical point. The insertion
of resistances, with a view to destroying part of the electro-motive force, does not
lead to any satisfactory results save in those cases where electrolytes are employed,
in connection with which a local action arises at the electrodes, and where
operations are conducted with a very weak current. This may be accounted for
by the fact that the local action under those circumstances acts more rapidly than
does the weak current. Thus, where the amount of current is exceptionally slight,
for example, a layer of lead sulphate may be obtained, in dilute sulphuric acid,
upon the lead anode. But where it is proposed to operate with comparatively
large amounts of current care should be taken to see that the source of current
exhibits precisely the requisite voltage, or that such voltage is secured by the
interposition of counter electro-motive force in the form say of polarizers, or
accumulators. The internal resistance of the cells thus interposed, and of the
source of current and conductors, should be as low as possible so as not to influence
the amount of current in an appreciable degree. Where more electro-motive force
is available a number of electrolytical cells may be connected in series care being
taken that all the cells are, as nearly as practicable, alike,, failing which totally
different products might be obtained in the several cells. Let it be assumed, for
example, that, in a number of cells with lead electrodes, the surface, or area, of
the anodes is considerably less than in the remaining cells: the consequence will
be, that on these smaller anodes, lead peroxide will form instead of lead at the
desired lower grades of oxidation; and similar alterations must be occasioned by
other variations, such, for example, as in temperature, density of the electrolyte,
and the like.
In lead plates of the Planté formation the difficulty has invariably been observed
that in a short time the positive plates became covered with a thin, though dense,
film of peroxide of lead whereby the electrolyte is precluded from any further
action penetrating the plates, so that it takes a very long period to complete the
electrode formation by that method. It was necessary also to reverse the current
at frequent intervals, that is to say to effect a series of oxidations and reductions,
in order to obtain a sufficiently deep layer of peroxide upon the plate.
prove
"
By my process electrode plates to be formed can in a very short time be covered
with a deep layer of oxide by the electrolytical process, According to this pro-
cess the cells should be connected to a source of current of a maxi-
mum electro-motive force of 2 volts. One storage cell will therefore
a sufficient source of electricity for one formation cell, or for
two such cells connected in series. The cells are subjected to the action of current
for a greater, or lesser, time according as a thin, or thick, layer of oxide is to be
obtained on the plate. After the lapse of the time allowed the plates will be
found to be covered with a perfectly firm and cohesive, though porous, layer of
oxide of lead. To accelerate the action it is advisable to raise the temperature
of the cell to about 40 degrees centigrade. This mode of treatment of the plates is
not however to be regarded as formation proper but as a preparatory operation, or
the initial stage of the formation process.
The plates covered with lead-oxide by this method may now be converted into
either negative, or positive, accumulator plates by further electrolytical treatment
by any suitable, or well-known, process. To enable the plates to be used as
negative electrodes all that is required is a subsequent reduction, say, in dilute

page_text: sulphuric acid, while, where positive accumulator plates are to be formed, the
plates should either be peroxydized directly, or first reduced-as in the case of
the negative plates-and then peroxydized. In this process of treatment the
whole of the preparatory layer of oxide becomes converted into peroxide in a
concrete form so that excellent positive electrodes are obtained as a result.
This process in an outcome of the observation that in electrolytical cells the
nature of the chemical compounds formed depends upon the voltage of the electro-
motive force while the quantity of chemicals produced in the course of the opera-
tion, in accordance with the well-known law, continues proportional to the amount
of current. A further feature of this process is, that in its performance, the lead-
oxide is not precipitated upon the electrodes from lead salts, but by the oxidation
of the metal of the electrode itself, it being immaterial what sort of electrolyte is
used.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
The preparation of electrodes for accumulators by the action of electric
currents, whose voltage does not exceed 2 volts per cell, and may be regulated
by insertion of counter-electro-motive forces without the aid of resistances,-for
the purpose of preventing the direct formation of peroxide and producing lower
stages of oxides on the electrodes, which can be subsequently transformed by the
usual treatment into positive and negative accumulator electrodes as hereinbefore
set forth.
Dad th 19th Ja. of Oetobar 1808
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.