Improvements in Secondary Batteries.
Year: 1896

page_text: Date of Application, 21st Dec., 1896-Accepted, 20th Mar., 1897
COMPLETE SPECIFICATION.
Improvements in Secondary Batteries.
I, ALBRECHT HEIL of Fränkisch Crumbach, Grand Duchy of Hesse, German
Empire, 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 :-
This invention relates to secondary batteries, and more particularly to the
construction or arrangement of a new or improved secondary battery cell, the chief
advantage of which is that it already possesses a primary potential inherent in
itself. By employing electrodes having different oxidation and chlorination values
the destruction during rest of the energy the battery has taken up, is prevented,
and it has also the property of being capable of being charged with stronger
currents than is the case with the accumulators or secondary batteries heretofore
known.
The action of the secondary batteries heretofore known is based, as is well
known, on the increase or decrease of the oxidation, chlorination or sulphation
values of the inetals in solutions by the charging and discharging of the electric
current, whereby a secondary potential is produced.
In the well known lead and sulphuric acid accumulators or secondary batteries,
one and the same metal i.e. lead, is employed for both electrodes. The two
electrodes have therefore the same oxidation value. In forming, either the one
or the other lead electrode can be employed indifferently as the positive or as the
negative electrode. Electro motive force is produced only when an electric current
from a separate source of electricity has flowed through a secondary battery
cell of that kind. The battery cell has therefore only a secondary potential which
is artificially produced, and which is consequently destroyed automatically by the
formation of local currents.
Secondary battery cells have already been constructed with electrodes of carbon
instead of lead and instead of sulphuric acid an electrolyte containing chlorine has
been employed.
The action of secondary battery cells of that kind is based on the secondary
potential produced by the oxidation or chlorination of one carbon or carbon and
peroxide of manganese electrode, and by the reduction of the other carbon or
carbon and peroxide of manganese electrode by means of current from a separate
or external source of electricity. Since also in that secondary battery cell both
electrodes.have the same oxidation and chlorination value, the energy taken up is
destroyed during rest by the formation of local currents. Further that kind of
secondary battery cell produces a very inconstant current, because during
discharge the highly oxidized negative peroxide of manganese electrode is
reduced whilst at the same time the less oxidized or reduced positive electrode
becomes very rapidly oxidized, thereby causing a rapid fall of potential.
For that reason, battery cells of that kind have been found of little value in
practical work.
Now a secondary battery cell constructed in accordance with the present
invention as hereinafter described does not possess those drawbacks, because it
possesses already a primary potential. The two electrodes employed therein have

page_text: different oxidation and chlorination values, so that there can be no destruction
during rest of the energy taken up.
The positive electrode of the secondary battery cell constructed according to the
present invention consists of sheet lead covered with powdered lead free from
oxide. The powdered lead may consist either of finely divided metallic lead, such
as that known commercially under the name of lead-dust, or of lead produced by
electrolytical process, the so called lead-tree or of reduced oxides of lead. The
negative electrode is made by reducing a carbon and peroxide of manganese
electrode in an electrolyte which contains chlorine but does not contain nitrogen,
by passing current through the same and then chlorinating by passing current in
the reverse direction.
A suitable method of reduction is as follows:-A carbon-manganese electrode
is arranged opposite a zinc electrode within a chloride electrolyte free of nitrogen
and these two electrodes are connected together until by the current thus produced
the carbon-manganese electrode has been reduced to a certain extent, for instance
until the manganese MNO, is reduced to MN,O,.
According to another method of reduction the carbon manganese-electrode is
arranged opposite an electrode consisting of only carbon in an electrolyte of the
kind above mentioned, and the current from an external source,-dynamo or other,
is passed into the carbon electrode and out from the carbon manganese electrode
until the desired reduction has taken place. Suitable electrolytes are:-a pure
magnesium chloride solution; a pure sodium chloride solution (common salt) or a
mixture of these two solutions.
The two electrodes thus treated are then placed in an electrolyte which contains
chlorine and which does not precipitate any metal when the secondary element is
being charged. Suitable electrolytes are pure ammonium chloride solution, pure
magnesium chloride solution, pure sodium chloride solution or a mixture of these
solutions.
If the two electrodes be now connected together, a powerful current is at once
produced which lasts until the powdered lead on the lead electrode is incapable of
taking up any more chlorine, and the carbon and peroxide of manganese electrode
has become reduced to a certain degree.
If the battery circuit be now opened the cell will at once reassume its original
primary potential which cannot be destroyed even by long contiuued short-
circuiting.
If now the battery cell be again connected with a source of current the cell will
at once take up electric energy again, the chlorine leaving the powdered lead and
being taken up by the peroxide of manganese and carbon electrode.
A special advantage of this secondary battery cell is constituted by the primary
potential which obviates the destruction by formation of local currents, during rest,
of the energy which has been taken up. The two electrodes used for this element
consist of lead sheet with lead powder, and of carbon manganese. Between these
two electrodes there exists as may be seen from the series of electrical potentials, a
natural difference of potential. In the usual lead secondary element the two
electrodes consist both of the same material (viz.: lead), therefore there is no
natural difference of potential between them, and such difference must be artificially
produced by forming or charging. It is now well known that in those batteries
the accumulated energy, if the battery is at rest, will be reduced in consequence of
the formation of local current, because these two electrodes possess no initial or
proper potential. This reduction of accumulated energy is entirely obviated in
this improved element as the electrodes, as above stated have a natural difference
of potential, which is constant and which has not to be produced artificially by
charging.
The element has further the property of being capable of being charged with
much stronger currents than can the accumulators or secondary batteries heretofore
known and also of being capable of being kept short-circuited without damage.

page_text: My improved battery cell does not require acid and can be constructed with
advantage as a dry cell designed to be constantly re-charged anew.
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 :-
A secondary battery cell in which a reduced and chlorinated peroxide of
manganese and carbon electrode is placed in a chlorine-containing electrolyte
opposite to a lead electrode that is covered with powdered lead, the arrangement
being such that the two electrodes alteruately give out and take up electrical
energy by their chlorination and reduction, according as they are discharged or
charged, substantially as described.
Dated this 21st day of December 1896.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.