Screening of lithium salts for use in lithium-ion batteries could give new direction to synthesis efforts.

Patrik Johansson, a computational chemist at Chalmers University of Technology, Gothenburg, Sweden, has shown how ab-initio calculations can be used to select lithium salts as candidates for use in battery electrolytes.  

Johansson focussed on finding salts whose anions have a low affinity towards lithium ions. The low affinity reduces the amount of ion-pairing, giving a high concentration of charge carriers in the electrolyte - an important property for potential batteries.  Johansson was expecting to find that large organic anions would give low lithium-ion affinities, but instead he discovered that medium-sized anions with nitrogen atoms at the lithium coordination sites gave the lowest affinities and so proved the most promising as electrolytes.  

The study involved about 50 different anions and their possible ion pairs, and used a range of computational strategies, including continuum solvent treatment and traditional gas-phase calculations. 

As a result of the study, Johansson recommends that future efforts to synthesise lithium salts are directed towards those based on the most promising heterocyclic anions.

Ian Gray