Aluminum-sulfur battery for small-scale storage at $8.99/kWh

A research team led by the Massachusetts Institute of Technology has developed a new type of aluminum–chalcogen battery that is purportedly resistant to dendritic shorting.

“The battery is intended for small-scale energy storage stationary applications,” researcher Donald R. Sadoway told pv magazine. “Commercialization is underway at US-based startup Avanti Battery Company.”

Dendrites are tiny, needle-like projections that can grow inside a battery, and cause a number of undesirable effects, including, in a worst case scenario, complete battery failure and even fires.

The battery relies on two electrodes made of aluminum and sulfur and a molten salt electrolyte placed between them. The electrolyte was composed of sodium chloride (NaCl), potassium chloride (KCl), and aluminum chloride (AlCl3), and formulated with high levels of AlCl3.

“We demonstrate that these are the key to supporting ultrafast electrodeposition of aluminium (cell charging) while vitiating dendrite formation,” the scientists said, in reference to the three compounds.

They are extremely cheap and earth-abundant compared to lithium, nickel, cobalt and graphite used in lithium-ion batteries.

“The chloro-aluminate salt that we chose essentially retired runaway dendrites, while also allowing for very rapid charging,” Sadoway explained. “We did experiments at very high charging rates, charging in less than a minute, and we never lost cells due to dendrite shorting.”

The researchers said the sulfur electrodes with a high loading of 12.0 mg cm2 can sustain a high capacity of 520 mAh g–1 more than 100 cycles at 5 C.

“We attribute full accessibility of electrode capacity to the advantageously low surface tension of the chloroaluminate melt,” they said.

The US team described the technology in “Fast-charging aluminum–chalcogen batteries resistant to dendritic shorting,” which was recently published in nature.

“Our battery has a two-fold economic promise. First, given the high earth abundance of all components, aluminum, sulfur, NaCl, KCl and AlCl 3, the estimated cell-level cost of our Al–S battery is as low as $8.99 per kWh, which is 12% to 16% of that of today’s lithium-ion batteries,” the academic said. “We also show that the use of low-grade aluminum (for example, food-packaging foil) in the negative electrode does not result in appreciable deterioration in cell performance.”

The research team included members from Peking University, Yunnan University, the Wuhan University of Technology, the University of Louisville, Oak Ridge National Laboratory, and the University of Waterloo.