The present paper proposes amethod to suppress the formation
of H2SO4 concentration difference in the electrolyte spaces near
the two electrodes during charge and discharge, leading eventually
to disbalance of the processes at the two electrodes of VRLABs.
This is achieved by the use of a three-layered absorptive glass
mat (AGM) separator, comprising a thicker AGM separator sheet
facing the positive plate, a thinner AGM sheet facing the negative
plate and a very thin AGM membrane inbetween. The AGM
membrane is processed with polymeric emulsion to acquire balanced
hydrophobic/hydrophilic properties and thus controls the
exchange rates of H2SO4, H+ ions, O2 and H2O flows between
the anodic and cathodic electrolyte spaces. Three types of polymeric
emulsions have been used for treatment of the membrane
and the test results evidence that the MMAGM membrane (i.e.
AGM modified with polytetrafluorethylene emulsion with addition
of “Luviskol”) sustains equal H2SO4 concentration in the two
electrolyte spaces, thus ensuring reversibility of the processes at
the two electrodes and hence longer battery cycle life. The other
two types of polymeric emulsions under test (polyvinylpyrollidonestyrene
–MPVS and polyvinylpyrrolidone “Luviskol” –MPVP) also
improve the reversibility of the charge and discharge processes at
the two electrodes, but with less contribution to the cycle life performance
of VRLA batteries. The results of this study prove that
the proposed three-layeredmembrane AGMseparator can be used
as an efficient component in VRLA battery design improving the
performance characteristics of valve-regulated lead-acid batteries.
References