Improvements in the Construction of Electrodes for Secondary Batteries.
Year: 1898

page_text: Date of Application, 28th July, 1898-Accepted, 11th Mar., 1899
COMPLETE SPECIFICATION.
Improvements in the Construction of Electrodes for Secondary
Batteries.
I, ALFRED HENNETON, of 152, Rue de Solférins, Lille, in the Republic of
France, Engineer, 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
In all forms of lead secondary batteries, the molecular action of the reactions
of charging and discharging gives rise to deformation and buckling of the elec-
trodes.
These deformations, apart from the danger which they constitute as regards the
durability of the elements, necessitate a very moderate utilisation of the current
which they are capable of giving, and consequently a considerable weight of
material.
The structure and form of the electrodes are the only causes of these defects.
The active portions of the electrodes are usually confined within massive and
rigid portions.
Such active portions, which are small and much divided, are necessarily sub-
mitted to a condition of expansion and increase in volume caused by the electro-
chemical action, and the rigid frame which encloses them (whether it be cast with
them or whether it be soldered thereto) opposes the normal course of such ex-
pansion.
It results from this that the electrode, if it is thin, not being able to elongate
its frame in order to find room, buckles; if it is thick, it pulverises and allows the
active substance to fall.
These defects have led me to endeavour to discover a type of electrode in which
the increase in volume is able to take place freely without any danger to the parts
of the secondary battery; which electrode is consequently capable of resisting the
strength of all rates of charging or discharging of which its capacity is capable.
Of all geometric forms the most simple and the most rational is the circle, and
it is likewise that in which the rate of expansion is the most uniform.
It is therefore the form which I have adopted and which, when completed by
the radial slit which I form in it, entirely fulfils the conditions above stated.
A circular form of electrode constructed according to my invention is illu-
strated in the accompanying drawing, the several figures of which are herein-
after described.
This circular form renders it possible whilst employing known elements, such
as smoothed and undulated or plaited lead ribband, to form a plate which is
perfectly uniform and of which the expansion is rendered perfect by means of
the radial slit which is made in it after soldering and formation.
This plate consists as shewn in Figure 1 of two lead ribbands, one being plain
or smooth and the other plaited or corrugated, the two being wound together
around an axis in such a manner as to produce a spiral consisting of ribbands in
contact.

page_text: This spiral having been formed, all the ribbands are soldered one to the other
along a radial line and the electrode is then formed. It only remains to provide
it with means of suspension and connection. For this purpose it is provided
with a head, which may resemble that shewn in Figure 2 in form.
A A are the points of suspension and B is a mushroom insulator for the elec-
trical connection.
The differences between the forms of electrodes shewn in Figures 3, 4 and 5 of
the drawing, consists 1st in the different forms of the supports A applicable to
the electrodes, 2nd in the arrangement of the saw-cuts or slits the object of which
is to impart the necessary elasticity to the electrode; the electrode in Figure 3
being slit at its lower portion, that in Figure 5 in its upper portion and that in
Figure 4 being slit vertically for its entire height.
As will be seen on reference to Figure 2, which shews part of an electrode there
will be seen a soldered joint «, commencing at the external circumference, con-
necting all the spirals one with the other and terminating at the internal circum-
ference, formed by the recess which has served for the passage of the axis for
winding the strips. This soldered joint is intended to support the electrode and
to receive the current carried by each strip.
It will be understood that the electrode which has just been described (if it is
regularly formed, which is the only case which should be considered) should
expand uniformly and without deformation upon the plane faces.
However, this uniformity in the mechanical action of increase in volume, can
only be obtained with positive plates if the plates are slit in the manner indicated.
The electrode obtained in the manner above stated, with reference to Figure 2,
receives a slight soldered joint al proceeding from the internal or centre to the
external circumference and in continuation of the soldering a already described
(see Figure 3); this soldering a¹ and also the spirals or convolutions are then slit.
Figure 4 shews an electrode soldered at a¹ and slit for its entire height; in
this case the soldering a which serves as a support is horizontal.
Figure shews an electrode the diametral soldering of which is slit at its
upper portion, each remaining portion of this soldering forming a support A.
Our electrode is thus a hinge and opens under the action of the increase in
volume in the same way that a pressure gauge tube opens under the action of
the pressure.
י
According to the use to which the batteries are to be put and their capacity, I
form my improved electrodes of very diverse dimensions, each one comprising one
or several spirals. In certain cases the mounting of the head which has been
described with regard to Figure 2 may be replaced by that shewn in Figures 4
and 5. In the same way, I may group two, three, four or a larger number of spirals
upon a supporting frame, without thereby in any way affecting the principle of my
improved electrode the characteristic feature of which may be said to consist in
suppressing the external frame within which the electrode is confined, establishing
its means of support and connection from the exterior towards the centre, and
giving to the active portions full freedom for extension.
Thus I may, without departing from this principle, give to my improved elec-
trodes a form different from the circular shape above described and make them
of the form of a square or of a polygonal shape having any number of sides.
On the other hand I may, without giving rise to any difficulty in construction,
form my electrodes of any thickness and of any dimensions, and I may form
their windings with smooth, plaited goffered or other bands, of a thickness which
is either uniform or variable, even in one and the same electrode.
I may likewise obtain my improved electrode by casting instead of by the
winding of ribbands. I may also impart to my electrodes their electrical capacity
either by chemical or electro-chemical formation, or by cementing.
My plate may be mounted in any desired manner, either by suspending the
electrodes vertically in the vessels, or by piling them horizontally, according to
the applications for which they are intended.

page_text: I have herein described several arrangements; those shown in Figures 2, 3 and
5, are for plates suspended vertically in the electrolyte, the holes A. A serving for
threading the plates upon the means of suspension.
With the electrode illustrated in Figure 4 on the other hand, the arrangement
of stacking the plates into a vertical pile may be adopted, in this case there are
two radial slots normal to the rigid band A. A upon which is soldered the current-
taker B.
It is obvious that other arrangements might be adopted, but, I would have
it understood that the details herein given as to the mounting of the electrodes
have been furnished only in order to render their utilisation comprehensible, and
that my invention relates only to the construction of the electrode properly so
called.
I may employ the form, dimensions and the number of unit elements per elec-
trode which are most suitable for the use to which it is to be put, for both fixed
and moveable batteries.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is:-
The improved electrode both as a whole and in its constituent parts having the
following characteristics:
a). The arrangement of the active metallic portion around a centre in a
uniform manner, either in circular or polygonal form, but without inactive
material in contact with all its external periphery.
b). The parts composing the electrode in (a) united and soldered one with
another in one or more directions radiating from the centre to the periphery.
c). The formation of a slit in the electrode in a radial direction in order to
constitute a hinge which still further facilitates the uniformity of the expansion.
7). The formation of this electrode by winding lead ribband, wires or tissue, or
by casting.
e). The electrical grouping of the parts one with the other, the source of cur-
rent being of any suitable kind.
Dated this 28th da
fT... 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.