%0 Journal Article
%T Ion Pairing Limits Crystal Growth in Metal每Oxygen Batteries
%J -
%D 2018
%R https://doi.org/10.1021/acsenergylett.8b01387
%X Aprotic alkali metal每oxygen batteries are promising high specific energy alternatives to Li-ion batteries. Growth and dissolution of alkali metal oxides such as Li2O2 in Li每O2 batteries and NaO2 and KO2 in Na每O2 and K每O2 batteries, respectively, are central to the discharge and charge processes in these batteries. However, crystal growth and dissolution of the discharge products is poorly understood, especially in aprotic electrolytes. In this work, we chose the growth of NaO2 in Na每O2 batteries as a model system and show a strong correlation between the electrolyte salt concentration and the NaO2 crystal size. With a combination of experiments and theory, we argue that the correlation is a direct manifestation of the strong cation每anion interactions, leading to decreased crystal growth rate at high salt concentrations. Furthermore, we propose and experimentally demonstrate that cation-coordinating crown molecules are electrochemically stable electrolyte additives that weaken ion pairing and enhance discharge capacities in metal每oxygen batteries
%U https://pubs.acs.org/doi/10.1021/acsenergylett.8b01387