Increasing the Cycle Life of Zinc Metal Anodes and Nickel-Zinc Cells Using Flow-Through Alkaline Electrolytes
Shuhua Shan, Mihir Parekh, Rong Kou, Donghai Wang, Christopher D. Rahn
Abstract
Alkaline electrolyte flow through porous Zn anodes and Ni(OH) 2 cathodes can overcome diffusion limits, reduce dendrite growth, and improve cycle life. Zinc deposition morphology improves with low flow rates electrolyte in KOH/ZnO electrolytes at current densities near the diffusion-limit regime. Zinc dendrites present without flow are suppressed by micrometer-per-second flow at concentrations ranging from 0.2 to 0.6 M ZnO dissolved in 6 M and 10 M KOH solutions. Zn-Cu asymmetric cell tests reveal that flowing electrolyte increases the lifespan by more than 6 times in the diffusion-limit regime by suppressing gas evolution and dendrite formation. Ni-Zn cell tests show that a flow-assisted battery cycles 1500 times with over 95% Coulombic efficiency (CE) at 35 mA cm −2 current density and 7 mAh/cm 2 charge capacity, increasing the battery lifespan by 17 times compared with a stagnant Ni-Zn cell. Flow-through electrolyte also stabilizes the Zn electrode in the over-limiting regime, achieving approximately 4 times increased lifespan and 297 cycles with over 90% CE at 52 mA cm −2 .