ZINC ELECTRODEPOSITION AND DENDRITIC GROWTH FROM ZINC HALIDE ELECTROLYTES.

Roughness evolution and dendritic growth restrict the thickness of electroplated zinc during the charge of zinc/halogen batteries and thereby impose operating and economic limitations on their application. A theoretical and experiemental study quantitatively characterizing roughness and dendrite evolution on zinc electrodes is reported. Comprehensive models were theoretically derived accounting for the initiation and for the propagation rates of dendrites in terms of system parameters including the current, applied potential, reaction kinetics, surface energy, macroscopic and microscopic geometry and convective flow. Morphological stability criteria were applied to define conditions under which electrodes are expected to remain smooth. The macroscopic current and potential distribution in flow cells were calculated and then coupled with analytical models for dendritic growth to provide the growth history and distribution of roughness elements along extended electrodes. Experimental studies of roughness evolution in electrodeposition under well-defined conditions were performed together with kinetic and transport measurements. Measurements and a study of the impedance of electrodes undergoing electrodeposition were conducted also.