IMPROVEMENTS IN SECONDARY BATTERIES AND IN RENOVATING OP DEVIVIRVING THEIR PLATES"
Year: 1883

page_text: LETTERS PATENT to Oliver Joseph Lodge D.Sc: of 26 Waverley Road,
Liverpool in the County of Lancaster, Doctor of Science and John Shield
Pattinson of 39 Falkner Square, Liverpool, aforesaid, Civil Engineer for an
Invention of "IMPROVEMENTS IN SECONDARY BATTERIES AND IN RENOVATING
OP DEVIVIRVING THEIR PLATES"
PROVISIONAL SPECIFICATION left by the said Oliver Joseph Lodge and
John Shield Pattinson at the Office of the Commissioners of Patents on the
20th February 1883.
OLIVER JOSEPH LODGE D.Sc. of 26 Waverley Road Liverpool in the County
of Lancaster, Doctor of Science and JOHN SHIELD PATTINSON of 39 Falkner
Square Liverpool aforesaid Civil Engineer " IMPROVEMENTS. IN SECONDARY
BATTERIES AND IN RENOVATING OR REVIVIFYING THEIR PLATES
"
Lead secondary batteries experience a constant slow loss of power, after having
been charged, whether they are allowed to produce a current or not; but when
they are producing a current their power falls off more quickly and recovers
somewhat when they stand idle again.
In addition to this there is a gradual diminution in their storing capacity after
having been in action-recharged and discharged-for some time. These deteriora-
tions it is one of the objects of the improvements hereinafter specified to obviate as
far as possible.
The cause of the slow loss of power when standing idle is partly due to local
action on the peroxidised or positive plate between the lead and the peroxide in
contact with it, by which the lead gets sulphated and the peroxide gets reduced to
litharge and possibly to sulphate.
The action is very slow however-and it is not permanent, for the sulphate
can be reperoxidised on recharging and the plate will become as good as ever.
The only permanent deterioration the positive plate is liable to is its thorough
peroxidation so as to leave no metallic connecting material-This might be avoided
by platinising the positive plate and depositing platinum black on the platinum
:

page_text: before coating it with minimum. But this would be expensive and it would
probably not last very long.
The changes which occur in the metallic or negative plate are much more
serious.
When standing idle the spongy lead decomposes the acid slowly and turns into
sulphate. But when producing a current the formation of sulphate goes on rapidly,
at the expense of the acid in the cell. The effect of this is then that the strength
of the acid decreases and that the plate gets crusted over with an adherent,
insoluble, non-conducting film which greatly increases the internal resistance and
decreases the acting surface, thus weakening the current.
This crust sometimes partially clears off when the cell stands idle and if the cell
be recharged the front layer of the crust is usually detached by the evolution of
nascent hydrogen from the metallic surface below it.
But when the sulphating action has penetrated deeper into the mass it is not
possible to get rid of all the sulphate in this mechanical way and since it is
insoluble in the battery solution, it is practically irreducible. Hence it accumulates
and the plate deteriorates.
To avoid this loss of power and deterioration it is necessary to be able:-
A:-to get rid of the sulphate when formed.
B-to delay or prevent its formation.
A. To get rid of the sulphate on an old reduced or negative plate, one plan we
use is to soak and to wash it in ammonic salts, or sodic byposulphite, or a hot
alkali, or in any such solution as will dissolve out the sulphate of lead. Another
plan is to put the plate in a solution in which sulphate of lead is soluble such as a
salt of ammonia, e.g. ammonic acetate, or in acetic acid or acetate of lead, and then
to electrolyse it-In this operation, which like that described at the beginning of
this paragraph must be conducted in a vessel other than the secondary battery cell,
the plate from which it is sought to remove the sulphate is used as the negative
plate: the positive plate being any other suitable plate. The sulphate of lead is by
these means reduced and reconverted into metallic lead.
It is doubtful whether immersion in such solutions would be good for the
positive or peroxidised plate of the battery; they might assist the local action
between its metallic lead and peroxide, by dissolving the protecting film of
sulphate. If they were found to do no harm to the positive plate however, both
plates might be immersed in a solution of ammonic salts or acetate of lead, or
other such solution and electrolysed as a preliminary to re-charging. In this way
old cells might be renovated.
B. To prevent the formation of sulphate. So long as hydrogen is plentiful in
the spongy metallic lead sulphate is not formed in any quantity and by the forma-
tion of nascent hydrogen a coat of sulphate may be quickly detached. Hence if
we can keep the negative plates well hydrogenised the insulating scum will not be
formed on them.
Metallic zinc immersed in the acid liquid of the cell and in metallic contact
with the lead is able to effect this. It keeps up a constant minute evolution of
gas and prevents the formation of any scum.
The zinc may be applied in various ways:-
1. As an electrolytic deposit in and upon the spongy lead.
This can be effected by filling the vessel in which the plates are to be formed
with a solution of pure or recrystallized sulphate of zinc and then applying the
charging current so as to decompose the sulphate of zinc depositing metallic zinc
at the same time as the litharge is reduced to load and liberating sulphuric
acid in the liquid. Or it may be effected by adding a solution of pure sulphate
of zinc to an already made cell while it is being re-charged,
2. As a plate rod or casting to support the litharge and spongy lead,
3. In the form of a zinc plate or rod or as an electrolytic deposit upon a zinc
plate or rod, no lead at all being used for the negative plate; the deposit is obtained
as in case 1.

page_text: 4. As an alloy of lead and zinc cast into a plate, rod, grid, perforated tube or
other form to support the litharge and spongy lead or active material.
5. As a distinct rod or plate of amalgamated zinc connected electrically with
the spongy lead plate and dipping into the same solution, not inserted during the
formation or recharging of the plates but only during their discharge or periods of
idleness. In all the above cases the zinc should be well amalgamated with mercury
and it is also of advantage that the lead of the negative plate be amalgamated;
and this can be done by adding to the solution, a solution of a salt of mercury
such as the sulphate, which is decomposed by the ordinary forming or recharging
current and the mercury deposited on the negative plate. When well amalgamated
the zinc is not rapidly attacked even though deposited in contact with lead.
When a zinc plate is used it is well to amalgamate it in the usual way before
putting it in the solution, but its amalgamation may be electrically replenished at
any time by the use of a suitable salt of mercury in solution, e.g. the sulphate. In
comparing the work of the cells above described with that of the ordinary type of
lead cell, it is found the N° 3 for example which probably gives the highest electro
motive force hardly shews any falling off in this particular during its discharge main-
taining the electro motive force steady till the cell fails on account of the exhaustion
of the positive plate instead of as at present the failure being caused by the
negative plate becoming exhausted long before the positive, the reason being
that sulphate of zinc being extremely soluble is dissolved off the face of the
negative plate as fast as it is formed and hence no clogging crust of any kind can
form on the negative plate. Thus the internal resistance is increased only as the
acid gets weaker and not in addition through the formation of an insoluble non
conducting crust.
N° 5 process revivifies temporarily exhausted cells more quickly. Amalgamated
zinc rods or scrap zinc in mercury may be arranged so as to be depressed into
the solution mechanically or to be connected with the negative plate, electrically.
whenever the battery shows signs of flagging, instead of coupling up more cells.
The zinc however applied should be in free electrolytic communication under the
liquid with the surfaces on which it is to act, and it must also be in metallic,
communication with them.
The gist of the matter is that a small area of zinc will keep a large area of lead
coated with hydrogen in such a way as to prevent the formation of sulphate of
lead.
Of course the deposited zinc gets slowly dissolved but its solution is decomposed
and the zinc again deposited during recharging.
If the discharge were continued so long that all the zinc were dissolved off:
the plate into solution the sulphate of lead would form and the plate become
clogged.
It is not desirable to discharge the cells so completely, but if it did happen, the
sulphate may be removed by subjecting the negative plates to process A.
The invention comprises the use in secondary batteries of a salt or salts of
Inercury in solution either alone or in conjunction with sulphate of zinc or other
metallic salts in order to amalgamate by means of the forming or charging current
the negative plate or any deposits thereon which if deposited under these conditions
are amalgamated as deposited.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Oliver Joseph Lodge and John Shield Pattinson in the Great Seal
Patent Office on the 8th August 1883.
OLIVER JOSEPH LODGE of 26 Waverley Road Liverpool in the County of
Lancaster Doctor of Science and JOHN SHIELD PATTINSON of 39 Falkner Square,
Liverpool aforesaid Civil Engineer "IMPROVEMENTS IN SECONDARY BATTERIES
AND IN RENOVATING OR REVIVIFYING THEIR PLATES
""
Lead secondary batteries experience a constant slow loss of power, after having
been charged, whether they are allowed to produce a current or not; but when
they are called upon to give a strong current their power falls off more quickly,
though it recovers somewhat when they stand idle again.
In addition to this there is a gradual diminution in their storing capacity after
having been in action-recharged and discharged-for some time. These deteriora-
tions it is one of the objects of the improvements hereinafter specified to obviate as
far as possible.
The cause of the slow loss of power when standing idle is partly due to local
action on the peroxidised or positive plate between the lead and the peroxide in
contact with it, by which the lead gets sulphated and the peroxide gets reduced to
protoxide and to sulphate.
The action is very slow however and it is not permanent for the sulphate is
reperoxidised on recharging without much delay or waste and the plate becomes as
good as ever.
The only permanent deterioration the positive plate is liable to besides mechanical
bending or warping is its thorough peroxidation through long continued over-
charging of the cell so as to leave no metallic connecting material; when this
happens the plate is apt to crumble to powder.
The changes which occur in the metallic or negative plate are more serious, and
it is commonly the negative plate which first fails in a cell and necessitates
recharging long before the positive plate is exhausted.
When standing idle the spongy lead decomposes the acid slowly and turns into
sulphate. But when producing a current the formation of sulphate goes on rapidly,
at the expense of the acid in the cell. The effect of this is that during dischargo
the strength of the acid decreases and the negative plate gets crusted over and
thoroughly impregnated with an adherent, insoluble, non-conducting film which
greatly increases the internal resistance and decreases the acting surface thus
weakening the current and causing the cell to fail.
The sulphate of lead crust when of any appreciable thickness is not easily or
completely reduced to metallic lead during the process of recharging, consequently
its amount tends to increase and the plate becomes ultimately clogged up with
sulphate of lead and has very little storage capacity left. By the continued action
of a weak charging current for a long time it is possible ultimately to reduce most
of the sulphate on such plates to metallic lead again; but it is a very slow process
and entails considerable waste of power in the evolution of gas; moreover the
positive plate is apt to become over-peroxidised while it is being done.
To sum up (1) The running down of a cell is ordinarily due to increase of
internal resistance caused by the sulphate of lead; and (2) the life of a cell is
shortened by the accumulation of sulphate.
To avoid this loss of power and this deterioration it is necessary to be able :-
A to get rid of the sulphate when formed. B: to delay or prevent its
formation.

page_text: A. To get rid of the sulphate on an old spongy lead or negative plate, one plan
we use is to soak and to wash it in ammonic salts, or sodic hyposulphite, or a hot
alkali, or in any such solution as will dissolve out the sulphate of lead, subsequently
rinsing with running water-Ammonic acetate is the most effective solution; and
a small quantity will serve again and again, for after it has become saturated with
the sulphate of lead it can be renewed and the sulphate of lead precipitated by the
addition of ammonic sulphate to it. If the dissolving out of the sulphate leaves
the plate porous or its coatings loose the interstices can be filled up by putting the
plate in a solution of acetate of lead with or without acetic acid and then electro-
lysing it in any suitable vessel, making it the negative plate and using any
convenient positive plate. Or a paste of litharge may be smeared over the cleansed
plate and forced into the interstices by any means, so that a subsequent application
of a charging current in a vessel of very weak sulphuric acid shall reduce it to
metallic lead as in the original "formation" of the plate and shall thus fill up the
pores and prevent the acid having too rapid an action on the too porous spongy
lead. Hydraulic or screw pressure may also be used to consolidate too porous
negative plates.
B. To prevent the formation of sulphate. So long as bydrogen is being liberated
by or upon the spongy metallic lead, sulphate is not formed, and by the liberation
of nascent hydrogen a thin or incipient coat of sulphate may be quickly detached.
Hence if we can keep the negative plates well hydrogenised the insulating scum will
not be formed on them.
Metallic zinc immersed in the acid liquid of the cell and in metallic contact with
the lead is able to effect this. It keeps up a constant minute evolution of gas and
prevents the formation of any scum.
The zinc may be applied in various ways:—
1. As an electrolytic deposit in and upon the spongy lead.
This can be effected by filling the vessel in which the plates are to be formed
with a solution of fairly pure or recrystallized sulphate of zinc and persulphate of
mercury in addition to the ordinary free sulphuric acid and then applying the
charging current so as to decompose the sulphate of zinc and sulphate of mercury
depositing metallic zine and mercury on the negative plate at the same time as the
litharge is reduced to lead and liberating sulphuric acid in the liquid. Or it may
be effected by adding a solution of sulphate of zinc and sulphate of mercury to an
already made cell while it is being recharged.
2. As a plate, rod or casting to support the litharge and spongy lead.
3. In the form of a zinc plate grid or rod or as an electrolytic deposit upon a zinc
plate grid or rod, no lead at all being used for the negative plate; the deposit is
obtained as in case 1, viz:-by the charging current applied to a cell containing a
solution of sulphate of zinc and sulphate of mercury together with some free
sulphuric acid.
4. As an alloy of lead and zinc cast into a plate, rod, grid, perforated tube or
other form to support the litharge and spongy lead or active material.
5. As a distinct rod or plate of amalgamated zinc connected electrically with the
spongy lead plate and dipping into the same solution, not inserted during the
formation or recharging of the plates but only during their discharge or periods of
idleness.
In all the above cases the zinc should be well amalgamated with mercury and it
is also of advantage that the lead of the negative plate be amalgamated; and this
is done by the addition to the solution of a solution of a salt of mercury such as the
sulphate, which is decomposed by the ordinary forming or charging current and the
mercury deposited. on the negative plate. When well amalgamated the zinc is not
rapidly attacked even though deposited in contact with lead. The mercury solution
we. commonly use is persulphate of mercury dissolved in hot or boiling dilute
sulphuric acid of specific gravity about 1100.
7:
When a zinc plate, rod or casting is used it is well to amalgamate it in the usual
way before putting it in the battery solution, but its amalgamation I
be
may

page_text: electrically replenished at any time by the use of a suitable salt of mercury in
solution, e.g. the sulphate.
In comparing the power of the cells above described with that of the ordinary
type of lead cell, it is found that No. 3 gives the highest electro motive force of any
practicable cell known and that when the cell fails it does so on account of the
exhaustion of the positive plate instead of as at present the failure being caused by
the negative plates becoming exhausted long before the positive, the reason being
that sulphate of zinc being extremely soluble is dissolved off the face of the
negative plate as fast as it is formed and hence no clogging crust of any kind
can form on the negative plate. Thus the internal resistance is increased only as
the acid gets weaker and not in addition through the formation of an insoluble
non-conducting crust.
It is important that the cell shall contain plenty of liquid so that all its free
acid shall not be turned into sulphate of zinc too soon.
N° 5 process revivifies temporarily exhausted cells inmore quickly. Amalgamated
zinc rods or scrap zinc in mercury may be arranged so as to be depressed into the
solution mechanically or to be connected with the negative plate electrically either
during the whole discharge, or during periods of rest or at times when the battery
shows signs of flagging, instead of coupling up more cells.
The zinc when applied as an appendage to a lead negative plate should be in free
electrolytic communication under the liquid with the surfaces on which it is to act,
and it must also be in metallic communication with them. It must never touch
the positive plate nor should the positive plate be amalgamated.
The gist of the matter is that a small area of zinc will keep a large area of lead
coated with hydrogen in such a way as to prevent or retard the formation of
sulphate of lead; or if used alone it keeps itself clean and has no tendency to form
an insoluble crust or filin.
Of course the zinc gets slowly dissolved but its solution is decomposed and the
zinc again deposited during recharging.
The invention comprises especially the use in secondary batteries of a salt or
salts of mercury in solution either alone or in conjunction with sulphate of zinc or
other metallic salts in order to amalgamate by means of the forming or charging
current the negative plate or any deposits thereon which if deposited under these
conditions are amalgamated as deposited.
Having now described the nature of our said invention and in what manner the
same is to be performed we declare that we claim :-
First The employment of ammonic acetate or other solution for the purpose of
cleansing old or sulphated negative lead plates of secondary batteries from a crust
of sulphate the pores left in the lead being subsequently filled up by the addition
of fresh litharge, or by electrolyzing acetate of lead and depositing the lead upon
the plates, or by pressure, as hereinbefore described.
Second-The employment of amalgamated zinc as an electrolytic deposit in
and upon the negative plates of secondary batteries, the zinc and mercury being
deposited out of a solution of a salt of zinc and a salt of mercury with or without
free sulphuric acid during the process of forming or during the recharging of a cell
as and for the purposes herein before described.
Third The employment of amalgamated zinc plates or rods to support the
litharge or lead salts and thus to constitute the negative plates of secondary
batteries as herein before described.
Fourth-The employment of zinc as the negative plates of secondary batteries,
the solution of the cell containing besides sulphuric acid and water sulphate of
zinc and sulphate of mercury which are decomposed and deposited in the metallic
form upon the zinc plate during charging, as herein before described.
Fifth The employment of an amalgamated alloy of lead and zinc cast into
grids or other form as carriers of the active material of the negative plates of
secondary batteries as hereinbefore described.
Sixth-The employment of amalgamated zinc as distinct plates or rods in

page_text: conjunction with the negative plates of secondary batteries and dipping into the
same solution for the purpose of revivifying the negative plates as hereinbefore
described.
Seventh-The employment of a salt or salts of mercury in solution to
amalgamate the negative plates of secondary batteries electrically while being
"formed" or when the cells are being recharged, as hereinbefore described.
In witness whereof I the said Oliver Joseph Lodge for myself and on behalf of
the said John Shield Pattinson have hereunto set my hand and seal this thirtieth
day of July One thousand eight hundred and eighty three.
OLIVER J. LODGE. (L.B.)