25 August 2019
Adapting aluminum for better batteries
Published online 30 November 2018
Modifying the surface chemistry of aluminum could promote significant advances in rechargeable battery technology.
An ultrathin chemical coating on aluminum could allow this abundant and inexpensive metal to be used in a new generation of efficient, cost effective and safe battery technologies.
“Aluminum has long been pursued as a prized candidate for high capacity, low cost electrical energy storage,” says Lynden Archer, leader of the research team at Cornell University in the U.S. that made the breakthrough. The work received some funding and research participation from Saudi Aramco.
Aluminum ions offer an electrical storage capacity up to four times greater than conventional lithium ion technology. Exploiting this advantage, however, has been hindered by aluminum oxide forming on the metal surface. This creates a barrier preventing the necessary electrical charge transfer processes.
The Cornell team found a way to coat aluminum with a thin chemical film that transforms the behaviour of the surface. The coating is added by treating the metal with a specific ionic liquid containing chloride ions and a small nitrogen-containing organic compound. Treated interface layers spontaneously erode existing aluminum oxide and also prevent any further oxide formation.
Crucially, electrodes carrying this specialized interface can work in batteries using water-based (aqueous) chemical solutions.
“The many fires widely reported in existing battery technologies stem from the flammability of the materials they contain,” Archer points out. Aqueous chemistry could avoid fire hazards while also providing the basis for more cost effective production.
The potential of the technology has already been demonstrated in small test systems.
Zhao, Q. et al. Solid electrolyte interphases for high-energy aqueous aluminum electrochemical cells. Sci. Adv. 4, eaau8131 (2018).