Yogesh Surendranath, Assistant Professor, Department of Chemistry

Li-O₂ batteries are poised to transform the consumer electronic and electric vehicle markets because they possess a theoretical energy density of 3,213 W h/kg, three fold larger than the current state of the art. This dramatic boost in energy density is provided by the carbon-based Li-O₂ cathode, at which O₂ is reduced to Li₂O₂ upon cell discharge. However, the insoluble Li₂O₂ precipitates indiscriminately on the surface of the carbon cathode, inhibiting subsequent reduction of O₂, leading to diminished capacity, poor rate capability, and poor round-trip efficiency. These challenges could be overcome if the surfaces of carbon cathodes can be modified to discourage the indiscriminate nucleation and growth of Li₂O₂ crystallites. We hypothesize that Li₂O₂ nucleation occurs via Li+ coordination to oxidic surface functionalities including ketones, carboxylic acids, and alcohols, which are known to be prevalent on carbon surfaces. Thus, we will apply well-known oxygen protecting group (PG) chemistries (e.g. silylation, benzylation, alkylation) to carbon electrodes to impede the nucleation of Li₂O₂ crystallites. By reducing the nucleation site density, fewer, larger Li₂O₂ crystallites will be favored, leaving the majority of the electrode surface available to sustain rapid O₂ reduction, thereby, enabling high energy and power densities.