Improvements in or relating to the Electrodes of Electric Accumulators.
Year: 1897

page_text: Date of Application, 10th July, 1897-Accepted, 14th Aug.,
1897
COMPLETE SPECIFICATION.
Improvements in or relating to the Electrodes of Electric
Accumulators.
I, ERNST WALDEMAR JUNGNER, of Engelbrechtsgatan 7 Stockholm in. the King-
dom of Sweden, Candidate of Philosophy, 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 electric accumulators in which the positive pole consists of metallic lead or
lead alloy, and which forms the negative bearer of a lead compound serving as the
active mass and in which the electrolyte consists of a sulphuric acid, there occurs
The surface of
always a local action between the metal and the aforesaid mass.
the metal is covered with sulphate of lead through the simultaneous action of the
sulphuric acid and of the peroxide of lead formed during the charging of the
accumulator. The reaction occurs according to the following formula:-
Pb+ PbO2 + 2 H₂SO = 2 PbSO4 + 2 H₂O.
This formation of sulphate has a very injurious action upon the accumulator and
must be regarded as the most serious drawback of the said accumulator. Owing
to this formation of sulphate the accumulator loses capacity and the tension
decreases when the accumulator is at rest. Furthermore there are increased
internal resistance and decreased power of action as serious results of this defect,
which moreover gradually destroys the metal. The present invention is devised
to remedy the above mentioned defect by means of the covering of the electrode with
a contact material, which has no action upon the materials of the accumulator or
the compounds which are formed. This is carried into operation by covering the
lead surface either by mechanical, chemical, or electrolytic means with a con-
ducting contact layer of peroxide of lead, between the molecules of which some
binding material without action upon the peroxide has been mixed. The prepara-
tion of the lead frame may be carried out in the following manner by way of
example:
The surface of the lead is painted over with a paint of lead oxide minium and
water and for the purpose of causing the paint to adhere better a solution of
sulphate of ammonia is added. After the paint has dried, when it forms a firm
coating adhering to the lead surface, the metal is placed as a positive electrode in
a solution of dilute sulphuric acid where it is allowed to remain until the lead
compounds have been entirely converted into peroxide. The metal treated in this
manner can then be dried, preferably by pressure under blotting paper and plunged
in a bath of boiling paraffin. After the paraffin has solidified the surface is care-
fully filed off. The layer of peroxide abovementioned might also be produced by
simply oxidising the lead surface by electric means to peroxide of lead, but in this
case of course a thinner layer is obtained.
The above mentioned production of the lead surface proves to be a good conductor
strongly adherent and unattackable by all the products which occur in the accumu-
lator, or are formed there, and as the electrolyte does not come into direct contact
with the lead surface local action in the electrode is entirely prevented.

page_text: Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what I
claim is
In positive electrodes of electric accumulators in which the inactive support con-
sists of metallic lead or lead alloy, and the electrolyte of a suitable acid, the
method of covering the surface of the metal by mechanical chemical or electrical
means with a conducting compact coating of peroxide of lead between the mole-
cules of which a suitable material is introduced for the purpose of binding the
same together substantially as described.
Dated this 101. Love of T..1.. 1007
W. P. THOMPSON & Co.
322, High Holborn, London W.C., Patent Agents for the Applicant.