Improvements in the Manufacture of Electrodes for Secondary Batteries.
Year: 1890

page_text: Date of Application, 14th May, 1890
Complete Specification Left, 16th Feb., 1891-Accepted, 28th Mar., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Electrodes for Secondary
Batteries.
A communication from Dr. PAUL SCHOOP, of Oerlikon, near Zürich, Switzer-
land, now residing at 53, Curtis Street, South Chicago, United States of
America.
I, WILLIAM LLOYD WISE, of No. 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Patent Agent, do hereby declare the nature of
this invention to be as follows :-
This invention has reference to the manufacture of electrodes for secondary
batteries and has for object to produce in a short time, at moderate cost, and with
a minimum waste of electric energy, electrodes having a high electric capacity,
without the use of paste or other material mechanically applied to the metallic
plate or body intended to form an electrode. For this purpose there are incor-
porated or combined with the plate at its surface certain elements or compounds
which when subsequently removed leave the said surface in a porous metallic con-
dition suitable for being charged in the ordinary manner for use as an electrode in
a secondary battery.
As suitable substances for carrying out this invention, there may be mentioned
fluorine, chlorine, and oxygen. Combinations or salts containing these elements are
also very effective as for instance perchlorate of potassium, chlorate of potassium,
chlorite of sodium and fluoride of ammonium.
One method of carrying out this invention is by electro chemical treatment of a
lead plate or body in a bath containing chlorate of potash and sulphate of ammonia.
For this purpose two lead plates (or two series of plates) are immersed in a bath
containing eight parts of water, twenty-eight parts of sulphate of ammonia and
one part of chlorate of potash. One plate is connected to the positive and the
other plate with the negative pole of an electric generator and an electric current
is passed through the bath and plates for a suitable time say about thirty-six hours.
For a plate having a surface of 100 square centimetres a current of of an ampere
may be used the temperature of the bath being maintained at 80° Fahrenheit.
Although these conditions are believed to be the most favourable ones for the
purpose, this invention is not limited to them as one or more or all of them may be
varied.
By this treatment there is first formed on the plate constituting the anode,
chloride of lead, which is afterwards decomposed by the current and changed into
peroxidised lead. It depends upon the conditions of the process how these changes
take place; if the electric current be strong, the quantity of chlorate of potash in
the bath be limited, and the temperature of the bath be comparatively high, these
changes will occur nearly simultaneously, the only visible result being the formation
of a black oxidised lead compound on the surface of the anode. The other plate,
constituting the cathode, is scarcely altered, hydrogen escaping freely from its
surface.
After this treatment the direction of the current is reversed so that the plate
which was formerly the cathode is now the anode and becomes coated with an
oxidized lead compound, whilst the plate which was formerly the anode but which
is now the cathode, becomes reduced by the hydrogen liberated thereon and so that
finally it is covered with pure spongy or porous lead.
When this has been effected
the bath or solution is removed from the vessel in which the plates were treated,
and after the plates have been washed the vessel is recharged with dilute sulphuric

page_text: acid (10 % acid) and the direction of the electric current is again reversed, the
current being passed through the bath and plates until gases are abundantly evolved
from each plate. The two plates (or two series of plates) or electrodes thus formed
are then ready for use in a secondary battery. As will be obvious the plate that
was first oxidized and then reduced, can be removed from the bath in which it was
treated, and after washing, be charged in the ordinary manner in a bath of dilute
sulphuric acid in a separate vessel. In its place in the first vessel a fresh plate
is suspended opposite to the remaining plate and then the current is again reversed,
so that the black oxidised compound upon the old remaining plate will be reduced
and assume the same spongy or porous condition as the first one and after washing
will be ready for the ordinary charging in a separate vessel.
The presence of sulphate of ammonia in a bath such as hereinbefore described,
allows of the use of many substances or salts for the purpose of incorporating
elements or compounds with lead which could not otherwise be used.
Thus, in the example given, the solution of chlorate of potash alone, would be
unsuitable for the purpose, for if an electric current were passed through such a
solution caustic potash would be formed at the cathode, from which lead would be
dissolved by the caustic potash, but if a sufficient quantity of the ammonia salt be
present, this action will not take place, owing to the formation of sulphate of
potassium and caustic ammonia, which will not attack the lead. Solutions contain-
ing fluorides also develope strong oxidizing qualities when used in the same manner
as the chlorine salt hereinbefore described, giving rise to the peculiar smell of
ozone in a most marked manner. Bromine and the iodine compounds may also be
used, but as is well known these compounds are at present more expensive than the
corresponding chlorine compounds. A bath containing a fluoride suitable for pro-
ducing electrodes according to this invention consists of one part of fluoride of
ammonia dissolved in two hundred parts of water. Into this bath the plates are
immersed and an electric current is passed through as before. Satisfactory results
may be obtained with a current strength of one ampere per 100 square centimetres
of surface of the plates; the temperature for the bath being 35° Fahrenheit, and
the duration of the process 100 hours. The result not only depends upon the
chemical character of the solution but also upon that of the electrodes.
In the case
of lead electrodes it is found, that lead containing small quantities of other metals,
such as zinc, copper, antimony, silver, and mercury, is easier to attack than pure
lead. The anode thus treated in the above mentioned bath is finally covered with
a layer of a black highly oxidised lead compound, whilst the cathode is scarcely
altered, hydrogen escaping freely therefrom. The current is then reversed and the
plates treated and finally charged in the manner hereinbefore described.
The thickness of the coating on the plate can be varied to suit requirements
according as it is required to make elements having a high rate of discharge or
elements having the highest possible electric capacity.
Dated this 14th dow of Man 1000
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Electrodes for Secondary
Batteries.
A communication from Dr. PAUL SCHOOP, of Oerlikon, near Zürich, Switzerland.
1, WILLIAM LLOYD WISE, of No. 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Patent Agent, 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 :→
1.
This invention has reference to the manufacture of electrodes for secondary
batteries and has for object to produce in a short time, at moderate cost, and with
a minimum waste of electric energy, electrodes having a high electric capacity,
.

page_text: without the use of paste or other material mechanically applied to the metallic
plate or body intended to form an electrode. For this purpose there is incor-
porated or combined with the plate at its surface one or other of certain electro
negative elements or compounds which when subsequently removed leaves the said
surface in a porous metallic condition suitable for being charged in the ordinary
manner for use as an electrode in a secondary battery. The electro negative sub-
stance used consists of one or other of the halogen elements chlorine, fluorine,
bromine or iodine. In carrying out the invention the lead plate or body is subjected
to an electro chemical treatment in a bath containing an electro negative halogen
compound as for examples a chlorate, chloride, fluoride or iodide of potassium,
sodium, ammonium, magnesium, calcium, manganese, chloric acid, hypochloric acid;
a salt of sulphuric acid as for examples a sulphate or bisulphate of ammonium,
sodium, potassium, magnesium, or a mixture of a sulphate and a bisulphate; and
water; with or without addition of free sulphuric acid, or chloro-sulphuric acid, or
sulphuric acid-mono-ethers. The composition of the bath, and the proportions of
with the
the several substances used therein to obtain the best results will vary
strength of current used and the temperature of the bath. A bath giving good
results can be made with one hundred parts by weight of sulphate of ammonia,
one hundred and forty parts by weight of dilute sulphuric acid (50% acid), seven
parts by weight of chlorate of potassium, and two thousand parts by weight of
water. Another bath, which gives good results can be made with one hundred parts
by weight of water, five parts by weight of bisulphate of sodium, and two-thirds
of one part by weight of chlorate of potassium. As will be obvious the latter
bath could be prepared by mixing distilled water, sulphate of sodium, chlorate of
potassium and sulphuric acid. In a bath thus prepared, two lead plates (or two
series of plates) are immersed one of the plates being connected to the positive,
and the other plate with the negative pole of an electric generator, and an electric
current is passed through the bath and plates for a suitable time say from about
thirty-six hours to one hundred hours according to the strength of current used, or
the depth of porous lead required. For a plate having a surface of 100 square
centimetres, a current of of an ampere may be used, the temperature of the
bath being maintained at 50° Fahrenheit. Although the nature and proportions
of the substances used, the strength of current, and the temperature of the bath
mentioned are believed to be the most favorable ones for the purpose, this inven-
tion is not limited to them as one or more or all of them may be varied.
By the treatment described there is probably formed on the plate constituting
the anode, chloric acid, part of which combines with the lead, forming chlorate.
of lead which is afterwards decomposed by the current, whilst the other part
The
is decomposed by the current without combining with the lead plate.
It depends upon
result is that an oxide of lead is formed upon the anode.
the conditions of the process how these changes take place; if the electric current
be strong, say about ampere per 100 square centimetres, the quantity of chlorate
of potash in the bath be limited say about 70% of the bath, and the temperature of
the bath be comparatively high say about 80° Fahr. these changes will take place
nearly simultaneously, the only visible result being the formation of a black oxidised
lead compound on the surface of the anode. The other plate, constituting the
cathode, appears to be scarcely altered, hydrogen escaping freely from its surface.
After this treatment the direction of the current is reversed, so that the plate
which was formerly the cathode is now the anode, and becomes coated with an
oxidised lead compound, whilst the plate which was formerly the anode but which
is now the cathode, becomes reduced by the hydrogen liberated thereon, so that
When this has been effected,
finally it is covered with pure spongy or porous lead.
the bath or solution is removed from the vessel in which the plates were treated,
and after the plates have been washed, the vessel is re-charged with dilute sulphuric
acid (10% acid) and the direction of the electric current is again reversed, the
current being passed through the bath and plates until gases are abundantly
evolved from each plate. The two plates (or two series of plates) or electrodes

page_text: thus formed and constituting positive and negative electrodes, are then ready for
use in a secondary battery. As will be obvious the plate that was first oxidised
and then reduced, can be removed from the bath in which it was treated, and after
washing, be charged in the ordinary manner in a bath of dilute sulphuric acid in a
separate vessel. In its place in the first vessel, a fresh plate is suspended opposite
to the remaining plate, and then the current is again reversed, so that the black
oxidised compound upon the old remaining plate, will be reduced, and assume the
same spongy or porous condition as the first one, and after washing will be ready
for the ordinary charging in a separate vessel. The plate, (or plates) after being
first oxidised can also be removed in this state from the bath in which it or they
were treated, and after washing, be reduced in the ordinary manner in a bath of
dilute sulphuric acid, or any other suitable solution for this purpose, as for instance
a solution of sulphate of ammonia, or bisulphate of sodium, or a mixture of these
substances with water in a separate vessel, and afterwards be charged in the ordinary
manner.
•
It has been found that to obtain the best results, the solution for forming (or
oxidising) the lead plates, should be kept preferably acidulated.
The presence of sulphate of ammonia in a bath such as hereinbefore described,
allows of the use of many substances or salts for the purpose of incorporating
elements or compounds with lead which could not otherwise be used. Thus, in the
examples given, the solution of chlorate of potash alone, would be unsuitable for the
purpose, for if an electric current were passed through such a solution, caustic
potash would be formed at the lead cathode, and dissolve a portion thereof, but if a
sufficient quantity of the ammonia salt be present, this action will not take place,
owing to the formation of sulphate of potassium and caustic ammonia, which will
not attack the lead.
Fluorine, bromine, and iodine compounds can also be used according to this
invention, but as is well known, these compounds are at present more expensive
than the corresponding chlorine compounds. A bath containing a fluorine compound
suitable for producing electrodes according to this invention consists of two parts of
fluoride of ammonia dissolved in one hundred parts of water. A small quantity, say
three parts by weight of sulphuric acid, or six parts by weight of bisulphate of
sodium may with advantage be added to the bath. Into this bath the plates are
immersed and an electric current is passed through as before. Satisfactory results
may be obtained with a current strength of from th to 1 ampere per 100 square
centimetres of surface of the plates; the temperature for the bath being 90°-100°
Fahrenheit, and the duration of the process 100 hours. The result however not
only depends upon the chemical character of the solution but also upon that of the
electrodes. In the case of lead electrodes, it is found that lead containing small
quantities of other metals, such as zinc, copper, antimony, silver, and mercury, is
easier to attack than pure lead. The anode treated in the manner described in the
above mentioned bath, is finally covered with a layer of a black highly oxidised lead
compound, whilst the cathode is scarcely altered, hydrogen escaping freely therefrom.
The current is then reversed and the plates treated and finally charged in either
of the ways hereinbefore described with reference to the plates treated in a solution
of a chlorine compound.
The thickness of the coating on the plate or electrode can in each case be varied
to suit requirements according as it is required to make elements having a high rate
of discharge, or elements having the highest possible electric capacity.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. In the manufacture of an electrode for a secondary battery subjecting a lead
plate or body to an electro chemical treatment such as hereinabove described in a
bath composed of an electro negative halogen compound, a salt of sulphuric acid,
and water, with or without addition of free sulphuric acid: as set forth.

page_text: 2. In the manufacture of electrodes for secondary batteries by electro chemical
treatment of a lead plate as set forth, the use of a bath composed of an electro
negative halogen compound, a sulphate or bisulphate, or both, and water, with or
without addition of sulphuric acid substantially as hereinbefore described.
3. The hereinabove described improved manufacture of electrodes for secondary
batteries.
D
1
W. LLOYD WISE,
Per F. J. Brougham.