A prototype zinc-polyiodide flow battery has been demonstrated with an energy density of 167 Wh/l (watt-hours per liter). Older zinc-bromide cells reach 70 Wh/l. For comparison, lithium iron phosphate batteries store 233 Wh/l. The zinc-polyiodide battery is claimed to be safer than other flow batteries given its absence of acidic electrolytes, nonflammability and operating range of that does not require extensive cooling circuitry, which would add weight and occupy space. One unresolved issue is zinc build-up on the negative electrode that permeated the membrane, reducing efficiency. Because of the Zn dendrite formation, the Zn-halide batteries cannot operate at high current density (>20 mA/cm2) and thus have limited power density. Adding alcohol to the electrolyte of the ZnI battery can slightly control the problem.