Electrodes go organic

A redox-active lithiated organic salt prepared from renewable resources has been used as electrode material for a lithium-ion battery

Credit: © 2009 ACS

Lithium-ion batteries have excellent energy density and are therefore attractive power sources for electric vehicles and portable electronic devices. However, they contain inorganic electrodes that are made from limited mineral resources through non-ecological, high-temperature processes. Research has recently focused on more sustainable materials, and oxocarbons, in particular, have shown promising properties as materials for positive electrodes.

Inspired by these results, Philippe Poizot at the University of Picardie Jules Vernes in France and co-workers have investigated¹ the tetralithiated oxocarbon salt Li₄C₆O₆. The researchers prepared the salt directly from tetrahydroxybenzoquinone, which can itself be made in aqueous solution from sugar found in plants. Alternatively, the salt could also be obtained by annealing the dilithium salt (Li₂C₆O₆) under an inert atmosphere. This solid-state disproportionation reaction, which occurred with sodium and potassium as well as with lithium, is unusual with organic compounds.

When it was tested as a material for the positive electrode in a lithium-ion battery, the Li₄C₆O₆ salt showed good electrochemical performance and reversibility. Furthermore, because it can be both reduced to Li₂C₆O₆ and oxidized to Li₆C₆O₆, it could also be used to construct a symmetrical lithium-ion cell. Although the operating voltage of this device is too low to be practical, chemical substitution offers various possibilities to tune the oxidation and reduction potentials.