Auxiliary WC electrodes in maintenance-free lead-acid batteries

In an attempt to develop a self-controlled lead-acid sealed system, WC auxiliary electrodes for maintenance-free batteries have been designed at LABD. The newly developed tungsten carbide catalytic electrode could replace the high cost noble metal (Pt, Pd, Ru) catalysts for the recombination reaction of hydrogen and oxygen to water.

WC auxiliary electrode. The WC catalytic electrode is partially immersed in electrolyte solution. The electrode comprises an electro-conductive lead grid onto which the catalytically active material is pressed. The catalytically active material contains: tungsten carbide (catalyst), active carbon, and teflonized carbon black as a binding substance. It has been established from previous researchers that WC has good catalytic activity toward hydrogen oxidation. LABD team has established that WC catalytic activity towards oxygen reduction is commensurable with its activity towards hydrogen oxidation. Active carbon increases the catalytic activity towards both the oxygen and the hydrogen reactions. WC recombination electrodes have half the catalytic activity of their Pt counterparts. To achieve the activity of Pt catalysts the surface area of WC electrodes should be twice as large as that of Pt ones.

Maintenance-free batteries with auxiliary WC electrodes. Lead-acid cells with WC catalytic devices have been designed and manufactured at the Lead-Acid Batteries Department. One WC electrode is connected by means of an electronic device to the negative plates of the cell in order to maintain oxygen reduction. The second WC electrode is connected through another electronic device to the positive plates for hydrogen oxidation. Both electronic devices are designed to maintain the potentials at which recombination of H₂ and O₂ proceeds at maximum rate. Operation of these cells is examined during battery charge, discharge, overcharge and on open circuit.

The results show that the use of auxiliary WC electrodes allows battery operation with no water loss. This method is especially suitable for stationary and load-leveling applications where battery maintenance (i.e. topping up with water) is a major problem.

References

1. G. Papazov, I. Nikolov, D. Pavlov, T. Vitanov, Lead-Acid Battery with WC Recombination Electrodes, Bulletin of Electrochemistry, 6 (1990) 255
2. Nikolov, G. Papazov, D. Pavlov, T. Vitanov, V. Naidenov, Tungsten Carbide Electrodes for Gas Recombination in Lead/Acid Batteries, J. Power Sources, 31 (1990) 69
3. G. Papazov, I. Nikolov, D. Pavlov, T. Vitanov, P. Andreev, M. Bojinov, Sealed Lead/Acid Battery with Auxiliary Tungsten Carbide Electrodes, J. Power Sources, 31 (1990) 79
4. G. Papazov, I. Nikolov, D. Pavlov, T. Vitanov, Application of WC Electrodes in Stationary Batteries, Proceedings TELESCON'94 Conference, Berlin, 1994, p. 463

Keywords: WC auxiliary electrodes, maintenance-free batteries, tungsten carbide, recombination reaction of hydrogen and oxygen to water, catalytic activity of WC, hydrogen oxidation at WC electrodes, oxygen reduction at WC electrodes