PNNL

Abstract

A Zinc-iodine flow battery (ZIFB) with super long cycle life, high energy, power density and self-healing behavior was presented. The long cycle life was achieved by employing a low-cost porous polyolefin membrane with optimized pore structure and stable electrolytes. The pores in the polyolefin membrane can be filled with a solution containing oxidized I3- that can react with zinc dendrite. Therefore, by consuming zinc dendrite, the battery can self-recover from micro-short circuiting resulting from overcharging the battery. By using KI and ZnBr2 as electrolytes and a high ion conductivity porous membrane, a very high power density can be achieved. As a result, the ZIFB exhibits an energy efficiency (EE) of 82% at 80 mA/cm2 and 71% at 140 mA/cm2, which is 8 times higher than the currently reported for ZIFBs. In addition, a long cycling life of more than 1000 cycles over 3 months with an energy density of more than 80 Wh/L was obtained at 80 mA/cm2. Furthermore, a kW-class cell stack with an output of 700 W was assembled and continuously run for more than 300 cycles. We believe this ZIFB with its high power density, long cycle life, and high reliability can lead the way to development of new-generation, high-performance flow batteries.