University of Córdoba researchers have built a zinc-air battery that uses vitamin B12 as a catalyst and completed up to 250 charge and discharge cycles in lab tests, according to a university release and a paper in the Journal of Materials Chemistry A.Zinc-air batteries draw oxygen from the surrounding air instead of storing it inside, which makes them lighter, the university said. Their water-based electrolytes don’t burn, and the type is already used in small devices such as hearing aids. Recharging is harder, because the catalyst, a substance that speeds up a chemical reaction, has to work during both discharge and charging.Vitamin B12, also called cobalamin, contains cobalt (III), a form of the metal cobalt. It dissolves easily in water, so it would wash out of a battery with a water-based electrolyte. The team fixed it to single-walled carbon nanotubes, extremely thin carbon tubes, the university said.How the vitamin stays in placeThe prototype comes from the Physical Chemistry research group at the university’s Chemical Institute for Energy and the Environment (IQUEMA). The paper describes chemically bonding the vitamin to the nanotubes, without the high-temperature treatment many catalysts need.Antonio Jesús Fernández Romero, a researcher on the team, said the vitamin “has proven to meet the necessary conditions to act as a good catalyst.” During discharge, it helps turn oxygen into water, and during charging, it promotes oxygen production, he said.Manuel Cano Luna, a study author, said the team looked to naturally occurring materials for new battery designs.The group has used biological molecules as catalysts twice before: hemoglobin, which contains iron (II), and catalase, which contains iron (III). Recharging is the new part.Other labs are chasing the same bottleneck. Chinese Academy of Sciences researchers made a graphene catalyst that raised a zinc-air cell’s round-trip efficiency to about 98 percent, and TU Darmstadt, the Technical University of Darmstadt, reported a spinel catalyst that kept a rechargeable cell running for more than 300 hours.What the cycling tests do and don’t showThe 250-cycle figure comes from small laboratory cells and does not mean the battery kept its starting performance throughout. The paper’s conclusions cite more than 250 cycles, but its results text reports data only to 235.According to XenoSpectrum, a science news site that analyzed the paper, the cells cycled in short steps of about six minutes of charging and six minutes of discharging. In a gel-electrolyte cell, discharge voltage was at least 1 volt at 180 cycles and at least 0.9 volts at 235 cycles, the site reported. It also said the charging reaction alone needed more voltage with the vitamin than with commercial cobalt oxide, 0.77 volts against 0.45 volts.The university said the result paves the way for cheaper, more sustainable storage of surplus renewable electricity. XenoSpectrum said durability under deeper charge and discharge still needs to be checked. No independent replication has been reported, the site noted. The release gave no timeline for further work. The study appeared in the Journal of Materials Chemistry A.