Improved Process and Apparatus for the Electrolytic Production of Porous Finely Subdivided Lead for use in Secondary Batteries.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improved Process and Apparatus for the Electrolytic Production of
Porous Finely Subdivided Lead for use in Secondary Batteries.
A communication by ERICH CORRENS, of 104/105, Alt Moabit, Berlin, in the
Empire of Germany, Manufacturer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool and 6 Bank Street,
Manchester, both in the County of Lancaster and 323 High Holborn, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this inven
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :—
For the better comprehension of the invention, reference is made to the accom-
panying sheet of drawings.
This invention. has for its object a process for the electrolytic production of
porous finely subdivided lead which is inserted as filling material in the lattice
framework serving as support for the active substances in secondary batteries.
This invention also relates to the deposits of other metals simultaneously produced
with the finely subdivided lead, which (metals) are soluble in sulphuric acid, and
finally to the amalgamation of the electrolytically deposited lead.
The process for producing this finely subdivided lead is conducted as follows-
Lead compounds are mixed in a pulverulent condition with diluted sulphuric
acid, sulphates, or even merely with water and a suitable combining material (such
as gelatine, glue or the like) and formed into plates of a given thickness. These
plates have a waffle like surface provided with conical ridges see Figure 1 on the
accompanying drawing; in order that the filling substance pressed into the plates
may be easily removed after the electrolytic treatment, the ridges are made with a
suitable inclination, see Figure 2.
The plates coated with the mixture herein before described are then immersed in
an electrolytic bath of diluted sulphuric acid or of the sulphates of the alkaline
earths, and the plates which cause the conveyance of the electrolytic current
placed opposite them. The positive pole of a source of current is then connected
with these last named plates, and the negative pole of the same is connected with
the plates holding the above named mixture, see Figure 3. The current is then
passed through until all the lead compounds are reduced to lead mud, which will
take place in one or more hours according to the thickness of the layer which is to
be converted.
In order to deposit other metals which are soluble in sulphuric acid simultane-
ously with the finely subdivided lead, the salts of the metals in question, such,
for instance, as iron, copper, zinc, tin, etcetera, etcetera, are mixed with the lead
compounds inserted in the waffle shaped plates. The simultaneous deposition of
the metals in question may also be produced by adding such metals or metallic
salts to the electrolytic liquid serving as a reducing bath, they being dissolved in
the same. On the reducing current being passed through the same, the metals in
question are in either case deposited simultaneously with the finely subdivided
Tead.
In order to avoid oxidation of the finely subdivided lead during its subsequent
treatment such as decanting, washing, grinding, etcetera, mercurial salts are added
to the liquid which serves as a reducing bath, or quicksilver is taken as the
positive electrode. A cathode composed of carbon or metal may also be coated
with mercury, this latter being dissolved and deposited on the negative electrode

page_text: (the finely subdivided lead which it is intended to produce). On the passage of
the reducing current each particle of the lead mud produced is then fully amalga-
mated on its surface.
When the substance inserted in the waffle like electrodes is completely reduced,
it is removed from the outwardly widening recesses and ground.
In order to render harmless the alterations of size towards the outside resulting
during the formation, suitable substances such as lime, lime salts or the like are
added to the pulverulent lead in a stirring apparatus, which substances may be
dissolved subsequently either direct by means of the electrolytic fluid or by means
of the current.
The mass prepared in this manner is then pressed into the lattice work which
serves as the support, and is afterwards exposed to the action of the negative
.current, in order that it may obtain a solid construction. The negative electrodes
are then ready for use, whilst the positive plates are simply exposed to the action
of the positive current to render them also ready for use. If other metals have
been deposited simultaneously with the finely subdivided lead, they are dissolved by
the oxidising action of the current. A little recess is thus formed in their place so
that the filling material is in this manner quite porous, and this takes place in pro-
portion to the lead super oxide formed.
For the electrolytic treatment the plates coated with the above named mixture
are either placed single to a suitable thickness in flat boxes, or they are placed in
the bath one above another or side by side in a larger number. In order to provide
a continuous process, the process is preferably carried out in the following manner,
which is shown in Figure 4 of the accompanying drawings.
The waffle shaped electrodes are formed as a thin continuous band which is
rendered sufficiently firm by means of cross ridges. This band B is conveyed on
rollers through a flat box A of considerable length which serves as a reducing
bath, whilst rollers c cause it with certainty to be immersed in the liquid. The
plate C serving to convey the positive current is arranged between the rollers c.
A cushion d is provided at the place where the continuous band B enters, over
which the substance is placed on the band B. A roller e then presses the sub-
stance against the plate so that it is conveyed through the bath in a firmly inserted
condition. The band B is then moved forward until a sufficiently strong current
has always entirely reduced the mass inserted therein by the time it reaches the
point of exit. Here it falls from off the band, in a manner which is easily
understood, and is then ground and further treated in the manner hereinbefore
described.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is-
1. A process for the electrolytic production of finely subdivided lead for use as
filling material for secondary batteries, characterised by lead compounds, which
are mixed with sulphuric acid, or sulphates, or water and a suitable binding material
(such as gelatine, glue, etcetera) being first plastered into waffle like plates and
exposed in an electrolytic bath to the action of the current until all the lead salts are
reduced, then the reduced mass being ground, and inserted in a moist condition in
the lattice work which serves as support for the active substance.
2. In the process described in Claim 1, the addition of metallic salts soluble in
sulphuric acid to the liquid which serves as the reducing bath, or to the lead
compounds originally inserted in the waffle like cathodes for the purpose of electro-
lytically depositing such metals simultaneously with the finely subdivided lead,
which metals are subsequently dissolved out again by the action of the electric
current so that the finely subdivided lead is rendered very porous and peculiarly
suitable for accumulating electricity.
3. In the process described in Claim 1, the addition of mercury or mercurial salts

page_text: to the liquid serving as the reducing bath with the object of amalgamating the
lead sludge formed down to its smallest particle and of thus preventing the forma-
tion of oxides.
4. An apparatus for carrying out the process described in Claim 1, consisting of
a flat box A of suitable length which serves as an electrolytic bath, through which
the continuous band B which serves as the waffle like plate, is passed over rollers,
the substance being placed on the band B at the point where it enters the box, and
pressed into it by means of a roller e, whilst the substance drops off the plate at
at the point of exit.
Dated this 23rd day of January 1893.
WM. P. THOMPSON & Co.,
Agents for the Applicant.