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11.2 Separators for Lead–Acid Storage Batteries 293

electrolyte, which have attained a commercial breakthrough in recent years, will be
the subject of a separate chapter.

11.2
Separators for Lead–Acid Storage Batteries
11.2.1
Development History

11.2.1.1 Historical Beginnings
The historical development of the separator and of the lead–acid storage battery are
inseparably tied together. When referring to lead–acid batteries today one primarily
thinks of starter batteries or forklift traction batteries, but the original applications
were quite different.
The very first functioning lead–acid battery was presented by Gaston Plant´ e
in 1860: spirally wound lead sheets served as electrodes, separated by a layer of
felt – the first separator of a lead–acid battery [12]. This assembly in a cylindrical
vessel in 10% sulfuric acid had only a low capacity, which prompted Plant´ eto
undertake a variety of experiments resulting in many improvements that are still
connected with his name.
Until about 1880 the lead–acid battery was exclusively the subject of scientific
study. Possible commercial utilization lacked suitable charging processes; sec-
ondary cells had to be charged by means of the primary cells already known at that
time.
Only with the discovery of the dynamoelectric effect and its rapid commercializa-
tion after 1880 did the industrial use of lead–acid storage battery begin. Here the
development of pasted plates by Camille Faure was essential for significantly raising
the amount of stored energy; they were separated by layers of parchment and felt
[13]. These batteries served predominantly for illumination and, later – beginning
around 1890, also as stationary batteries for peak power load leveling in power
plants. Glass rods frequently sufficed as spacers, or these batteries were even built
without separators at all, simplifying the frequent removal of anode mud from the
containers.
The development of the tubular plate during the last decade of the nineteenth
century required oxidation-and acid-stable porous material. Of the natural materials
only a few are moderately stable in sulfuric acid: glass, asbestos, rubber, and
cellulose. All have been tested, singly or in combination. Asbestos fabrics as
tubular material for positive electrodes, textiles for fixing the negative mass, and
rubber rods as spacers were in the first batteries for driving electric vehicles, an
application becoming popular in that period. These vehicles, however, required
increased energy densities, that is, the electrode distance had to be decreased. After
many trials, extruded hard rubber tubes prevailed for the positive electrodes, with
finely sawn cross-slits to allow ion migration. At that time the first wooden veneers