Scientists at the US Naval Research Laboratory and battery technology developer EnZinc announced on April 27 they had developed zinc-based batteries as “a safer alternative to fire-prone lithium batteries”, which have recently been banned in some applications from US Navy ships and other military platforms.

The key to the research is the development of a three-dimensional zinc sponge, which replaces the traditional powdered zinc anode and allows the batteries to recharge — a major advantage over traditional zinc batteries, which cannot recharge because they form dendrites that can grow to cause short circuits. Bismuth and indium is added to help control chemical reactions, but not strictly required, EnZinc president Michael Burz told BESB.

“The primary solution is the structure,” he said.

Burz said that several criteria had to be met before the technology could be taken further, and they had all met requirements. The criteria included material strength, electrolyte combinations, cell lifetimes, cycle life and scale of production.

“It will very much be able to compete with lead-acid,” said Burz. “We estimate that where a lead battery costs $130 per kilowatt hour, a zinc one will cost around $150 – with twice to three times the energy and a much longer life and half the weight.

“It’s also totally recyclable.”

In findings published in the journal Science, the researchers said they had achieved extended lifetimes in single-use cells; cycled cells more than 100 times at an energy content that was competitive with lithium; and cycled cells more than 50,000 times in short-duty cycles with intermittent power bursts. (This is much in the way that batteries are used in some hybrid vehicles.)

“We can now offer an energy-relevant alternative, from drop-in replacements for lithium-ion to new opportunities in portable and wearable power, and manned and unmanned electric vehicles while reducing safety hazards, easing transportation restrictions, and using earth-abundant materials,” said Jeffery Long, from the NRL’s advanced electrochemical materials group.

“Our team at the NRL pioneered the architectural approach to the redesign of electrodes for next-generation energy storage,” said Debra Rolison, senior scientist and principal investigator on the project. “The 3-D sponge form factor allows us to reimagine zinc, a well known battery material, for the 21st century.”

According to Burz, the new technology would have a large range of applications. “Large battery-powered electronics from electric vehicles to home energy storage will be able to be powered by cleaner, fully recyclable zinc-based batteries – and they’ll carry none of the fire risk of lithium-based batteries,” he said.

“The size that we are going to shoot for will be cells of two inches by two inches that we put into a quilt pattern, which then means we can scale them up to very, very large sizes.

“This breakthrough in rechargeable battery technology means that zinc has the potential to displace lithium because it is a safer, more affordable, and more readily available material.”

Burz says EnZinc plans to have a battery ready for production by the end of 2019.