While useful in non-rechargeable applications – it is the basis for ‘alkaline cells’ – zinc electrodes tend to grow dendrites (whiskers) when charged, wrecking the cell.
Scientists at the US Naval Research Laboratory (NRL) have created nickel-zinc batteries with 3D sponge zinc anode instead of powdered zinc.
“The key to realising rechargeable zinc-based batteries lies in controlling the behaviour of the zinc during cycling,” said NRL researcher Joseph Parker. “Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites.”
The monolithic zinc sponge anodes can be cycled in nickel–zinc alkaline cells hundreds to thousands of times without undergoing passivation or macro-dendrite formation, according to the abstract of ‘Rechargeable nickel–3D zinc batteries: An energy-dense, safer alternative to lithium-ion‘, published in Science.
According to the Lab, three demonstrations have been made using the material:
- >100 high-rate cycles at 40% depth of zinc discharge at “an energy content competitive with lithium-ion batteries”.
- > 50,000 times in short duty-cycles with “power duty cycles required for start-stop micro-hybrid vehicles” .
- >90% theoretical depth of zinc discharge in a non-rechargeable cell
Nickel-zinc alkaline is seen as a less fire-prone alternative to lithium-ion cells, which have been banned for some US military applications, according to NRL.
Meinrad Machler and EnZinc are industrial partners in the project.