Substrate materials for bipolar lead/acid batteries

Attempting to develop a composite substrate for a bipolar lead/acid battery, more than 120 ceramic materials were screened. About 60 of them having a conductivity greater than 10 Ω−1 cm−1 and cost less than US$ 1/g were tested. Test methods and devices were developed to examine the chemical and electrochemical stability of the filler materials, oxygen and hydrogen overpotential, and porosity of a composite substrate made of polyethylene with dispersion of the conductive filler. Very few of the ceramic materials we tested possess the desired stability, high oxygen/hydrogen overpotential and imperviousness to the acid electrolyte. Silicides of Ti, Nb and Ta appear to be acceptable fillers for plastic composite substrates. These composite substrates, however, lacked of paste adhesion and were heavy. The properties of these conductive fillers and directions for improvement in the development of a bipolar substrate are discussed.