Improvements in or relating to the Negative Elements (Positive Electrodes in Charging Secondary Cells) of Voltaic Batteries.
Year: 1891

page_text: Date of Application, 6th June, 1891
Complete Specification Left, 7th Mar., 1892-Accepted, 9th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Negative Elements (Positive
Electrodes in Charging Secondary Cells) of Voltaic Batteries.
I DESMOND GERALD FITZ-GERALD, of 46 Loughborough Road Brixton in the
County of Surrey Electrician do hereby declare the nature of this invention to be
as follows:
"
.
In voltaic elements where peroxide of lead (or a lead compound to be converted
into peroxide of lead) is held on, or in, a grid, or other support, of lead or lead
alloy, the conditions for objectionable "local action are, more or less, present
owing to the peroxide and the metal being in contact with each other, and with
the electrolyte. This local action is detrimental to the working, and to the per-
manency, of the element owing to a wasteful conversion of the peroxide into lead
sulphate, or the "running down" of the element, whether the external circuit be
open or closed; and also owing to the simultaneous conversion of the lead, in the
metallic support, into lead sulphate; in action ultimately resulting in the destruction
of the support, and further, owing to the production of a layer of lead sulphate
between the "active material" or peroxide of lead and the metallic support, which
layer has the effect of increasing the resistance of the element, or limiting the rate
of discharge obtainable with it.
My invention has for its object to increase the efficient working condition of the
metallic supports of such elements, and to obtain greater economy in the working
of the battery by obviating local action in the elements. This I effect according
to my invention by coating the grid, or support, of lead, or lead alloy, with gold or
with platinum, or with platinum superposed upon gold, which coating is preferably
effected by means of electro-deposition. I have found that it is not necessary that
such coating should be of considerable substance, or that it should be perfectly
continuous, but that a very slight layer, and even an imperfect coating, of the
protective metal, or metals, greatly improves the contact between the metallic
support and the active material in, or upon, it, whilst by preventing, or
impeding, contact between the oxidisable metal and the electrolyte it reduces, or
obviates, local action.
ليم
1
1001
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in or relating to the Negative Elements (Positive
Electrodes in Charging Secondary Cells) of Voltaic Batteries.
I, DESMOND GERALD FITZ-GERALD of 46 Loughborough Road, Brixton in
the County of Surrey, Electrician, 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 :-
In voltaic elements where peroxide of lead (or a lead compound to be converted
into peroxide of lead) is held on or in a grid, or other support, of lead, or lead
alloy, the conditions for objectionable "local action are, more or less, present
owing to the peroxide and the metal being in contact with each other and with
the electrolyte. This local action is detrimental to the working, and to the per-
manency, of the element owing to a wasteful conversion of the peroxide into lead
running down" of the element, whether the external circuit be
sulphate, or the

page_text: open or closed; and also owing to the simultaneous conversion of the lead, in the
metallic support, into load sulphate; an action ultimately resulting in the destruc-
tion of the support, and further, owing to the production of a layer of lead
sulphate between the "active material or peroxide of lead and the metallic
support, which layer has the effect of increasing the resistance of the element, or
limiting the rate of discharge obtainable with it.
The explanation of the fact that this local action occurring between substances
so far apart on the electro-chemical scale as peroxide of lead and metallic lead is
not very much more violent and rapid than it is found to be in practice, has by
some been referred to the presence of this layer of sulphate, which, if perfectly
continuous and covering the whole surface of the support, would render the element
ineffective. The same fact has by others, been explained by the electrolytic
resistance of the local circuit i.e. by the effect of the dense layer of peroxide
which, when the element is perfectly "charged" forms upon the metallic support,
and, whilst the said layer remains intact, almost completely impedes the contact
between the support and the electrolyte which is essential to the production of the
local currents.
My invention has for its object to increase the efficient working condition of the
metallic supports of such elements, and to obtain greater economy in the working
of the battery by obviating local action in the elements. This effect according
to my invention by coating the grid, or support, of lead, or lead alloy or the
portions thereof which are to be in contact with the active material or material to
be rendered active with gold, or with platinum, or with platinum superposed upon
gold, which coating is preferably effected by means of electro-deposition. I have
found that it is not necessary that such coating should be of considerable substance,
or that it shloud be perfectly continuous, but that a very slight layer, and even an
imperfect coating, of the protective metal or metals greatly improves the contact
between the metallic support and the active material in, or upon it, whilst, by pre-
venting or impeding contact between the oxidisable metal and the electrolyte it.
reduces, or obviates local action.
In carrying out my invention I prefer to take the grids or supports just after
casting; but in many cases it will be found necessary to render them perfectly
clean which may be done by immersing them in dilute nitric acid; (the proportions
may be one part by weight of strong acid to ten parts by weight of water) and
prior to the use of the acid, it is necessary, if grease be present, to remove it from
the surface by immersion in a weak hot solution of caustic or carbonated alkali
and subsequent washing in water.
The anodes used should be of "fine" gold. When anodes in the form of plates
or sheets of gold are employed, and when the interior surface of the alveolar
recesses or apertures in the " grid or support require to be coated, two such
anodes should be used one on each side of the grid or the like, and these anodes
should be placed at a considerable distance from the respective sides. Thus, the
distance between each anode and the grid or support may advantageously be from
5 to 6 inches, or more; the object being to equalize the resistances of the paths
between the anode, and the exterior and interior surfaces respectively, which are
to be coated. But since it is of greater importance to gild the interior surfaces of
the alveolar recesses or apertures than it is to gild the external surface of the
support, I have found it advantageous to make the anode of a number of gold or
gilt pins or projections corresponding to the number of apertures or recesses in
the grid or support, within which these pins or projections are to be inserted.
These pins or projections may advantageously be of platinum wire to be gilded
and passing through, and held by a plate of metal insulated from the gilding
solution. Thus a plate of brass or copper of about the same size as the grid or
support to be prepared may have a thin sheet of ebonite, gutta percha or other
insulating material cemented to one of its surfaces. The compound plate is then
perforated with perforations corresponding to the centres of the recesses or aper-
tures in the grid or support, and through these perforations short pieces or pins of

page_text: platinum wire may be passed, in such manner as to fit tightly within the perfora-
tions and thus to make contact with the metal plate, and the compound plate may
then be cemented to the bottom of an ebonite tray with the pins projecting
outward. After establishing contact with the metal plate by means of an
insulated wire, a varnish may be applied to prevent the gilding fluid from coming
into contact with the metal plate through the perforations in the insulating
material.
The advantage of providing the anode with pins of platinum to be gilt instead
of gold is obvious when the question of the permanency of the anode is considered..
The platinum pins, prior to their use as the anode may be gilt by electro depositions
from the cyanide bath hereinafter mentioned. During this gilding process they
constitute a cathode; the anode then being a plate or wires of gold. The quantity
of electricity (current multiplied into time) should be about the same for each
process of deposition, i.e. for that of the gold upon the platinum pins and for that
of the gold upon the "grid" or other support.
The gilding solution I prefer for the sake of convenience to use is one that can
be used cold, such as a solution of about 6 parts by weight of cyanide of potassium
in 160 parts by weight of water, which should contain less than one part by weight.
of gold in the condition of cyanide. This solution of gold can readily be made by
the "battery process" in which process it may be found convenient to replace the
usual gold cathode by a plate of lithanode. The cold gilding solution of Roseleur
also gives good results. The most perfect coating is obtained however by the use
of a hot, and somewhat dilute cyanide solution of gold; this may contain from
8 to 12 ounces of cyanide of potassium and 1 ounce of gold to the gallon of water
and may be used at a temperature of from 140° to 150° Fahrenheit.
It is also expedient to coat with gold or platinum or with platinum upon gold
those portions of the support which are outside the electrolyte but exposed to the
oxidising action of air and of acid spray and especially those portions at which
contact is made between the cells.
Although a very slight and even imperfect coating of gold upon the surface of
the grid or support to contain the peroxide active material, will generally be found
to be permanently effective in augmenting the rate of discharge of a lead accumu-.
lator and in obviating the rise of resistance, I sometimes find it advantageous to.
superpose a coating of platinum upon the gold more especially where local action
requires to be totally obviated, or where the presence of chlorides in the electrolyte.
may possibly occur. For this purpose Roseleur's well known solution of platinum
may be employed. Or platinum may be deposited directly upon the lead or lead
alloy for instance by means of a solution of platinic chloride in a strong solution.
of potassic cyanide. With this a platinum anode exposing a large extent of surface
should be used.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
In or for voltaic batteries wherein a grid or the like of lead or lead alloy,.
supports or carries the active material or material to be rendered active; a negative
element (positive electrode in charging secondary cells) in which the grid or the
like is coated or partly coated with gold or platinum or with platinum upon gold.
substantially as hereinbefor described.
L
1002
J. H. JOHNSON & Co.,
Agents.