## Study identifies halogen-free superhalogen electrolytes for Li-ion batteries

##### 25 October 2014

Most electrolytes currently used in Li-ion batteries contain halogens, which are toxic. An in-depth study based on first-principles calculations by researchers at Virginia Commonwealth University has shown that the anions of commercially available electrolytes for Li-ion batteries are all superhalogens. With this knowledge, they identified several halogen-free less-toxic superhalogen electrolytes with comparable performance characteristics. Their paper is published in the journal Angewandte Chemie International Edition.

In the search for halogen-free electrolytes, we studied the electronic structure of the current electrolytes using first-principles theory. The results showed that all current electrolytes are based on superhalogens, i.e., the vertical electron detachment energies of the moieties that make up the negative ions are larger than those of any halogen atom. Realizing that several superhalogens exist that do not contain a single halogen atom, we studied their potential as effective electrolytes by calculating not only the energy needed to remove a Li+ ion but also their affinity towards H2O. Several halogen-free electrolytes are identified among which Li(CB11H12) is shown to have the greatest potential.

—Giri et al.

The researchers hope that the findings will lead to production of safer, less toxic batteries. They also found that the procedure outlined for Li-ion batteries is equally valid for other metal-ion batteries, such as sodium-ion or magnesium-ion batteries.

The significance [of our findings] is that one can have a safer battery without compromising its performance. The implication of our research is that similar strategies can also be used to design cathode materials in Li-ion batteries.