Experimental Validation of the Elimination of Dendrite Short-Circuit Failure in Secondary Lithium-Metal Convection Cell Batteries

Sustained cycling of metallic lithium negative electrodes is possible without dendrite failure in the convection battery due to the ability to effectively lower concentrations within the separator region during charge by flowing electrolyte through the negative electrode first, where lithium ions are consumed, prior to entering the separator. Consumption of lithium ions prior to entering the separator region results in a lowered concentration and reduced electrochemical potential. Additionally, convective flow reduces overall concentration gradients therefore lowering concentration overpotentials. At these lowered concentrations, dendrite formation is not thermodynamically favored as shown through the relationship between concentration, electrochemical potential and Gibbs free energy. This work presents theory, experimental validation, and autopsy (visual) verification of how the pumping of electrolyte between counter-electrodes eliminates dendrite short-circuit through the separator. Experimental validation included establishing a control using lithium particles as the negative electrode. The control consistently failed due to dendrite-based short circuit when operated without the flow of electrolyte. For the same experimental system operated with flow, the battery operated for 10 cycles (limit of study), exhibiting characteristic capacity fade at these rates. Imagery confirmed that dendrite crystals were not forming in the separator when operated during flow and that crystals did form without flow. (C) 2014 The Electrochemical Society. All rights reserved.