Zinc is commonly used in single-use batteries, but it hasn't been a very good option for rechargeable cells in the past because the materials can form conductive dendrites over time and cause equipment to short circuit. The NRL's method, which is detailed in a new paper published in the journal Science, uses a specially designed "3D sponge" on the Zinc anode to distribute currents more uniformly and prevent dendrites from forming in the first place. In addition to extending the lifetime of single use batteries, the NRL found that their new Ni-3D Zn cells were competitive with lithium-ion batteries over more than 100 recharge cycles. The batteries also performed comparably to lithium batteries when run through more than 50,000 "short duty" cycles interspersed with short power bursts to simulate hybrid vehicle applications. Because they have a lower weight than lithium cells of comparable capacity, the Ni-3D Zn cells could even help hybrid or electric vehicles stretch their range.
The NRL says their research is complete and the 3D zinc sponge technology is "ready to be deployed within the entire family of Zn-based alkaline batteries" in both military and civilian applications. San Francisco-based battery company EnZinc, which worked with the NRL on the paper, estimates the first batteries using this technology will be on the market by the end of 2019.
"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," the NRL's Dr. Jeffrey Long said, "while reducing safety hazards, easing transportation restrictions, and using earth-abundant materials."
Update: This post has been edited to add a time-to-market estimate from EnZinc.