Effects of preparation condition and particle size distribution on fumed silica gel valve-regulated lead-acid batteries performance

The effects of three types of fumed silica on the electrochemical properties of gelled electrolytes have been investigated by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscope (TEM) and the Brunauer, Emmett and Teller (BET) technique. The CV and EIS results show that a moderate mechanical dispersion of fumed silica in the H2SO4 solution has important effects on the electrochemical properties of the gelled electrolyte. The optimal mechanical dispersion time is closely related to the operating temperature during preparation of gel, as well as the silica particle size and its distribution. A high stirring rate improves the electrode capacity and decreases the viscosity of the gelled electrolyte. With moderate mechanical dispersion, gelled electrolytes prepared from different fumed silica particles exhibit equal electrode capacities. (C) 2008 Elsevier B.V. All rights reserved.