A tubular electrode is devised and filled with PbO, powder produced by grinding the active material obtained on a lead-grid plate. The spine of the tubular electrode is isolated in such a way that its contact with the H,SO, solution is realized only through the pores of the active material. The effect of additions of antimony, arsenic and bismuth (introduced in the spine alloy or into the solution) on the rebuilding processes of the active-material structure is investigated. A critical density of the PbO, powder is determined below which restoration of the active-material structure is not possible. The investigations show that dopants decrease the value of the critical density; their impact is in the order antimony > bismuth > arsenic. This effect constitutes one of the basic features of the 'antimony-free effect'.
Editorial note.
Although the experimental data discussed here has been reported by the author in a previous issue of this Journal (Journal of Power Sources, 30 (1999) 117-129). he now presents an extended interpretation of the findings, including the new concept of dopants acting as 'electric bridges'. The work aroused considerable interest at the Conference.