Low discharge capacities resulting from electronically insulating Li2O2 film growth on carbon electrodes is a major impediment to Li-O2 battery commercialization. Redox mediation is an effective strategy to drive oxygen chemistry into solution, avoiding surface-mediated Li2O2 film growth and extending discharge lifetimes. However, in order to continue improving upon prior research, exploration of more redox mediators and discovery of new redox mediator selection criteria is required. Herein, we report a new class of triarylmethyl cations which are effective at enhancing discharge capacities up to 26-fold. We observe that more positive redox mediator reduction potentials, and thus more sluggish kinetics for reaction of redox mediator and oxygen, leads to larger discharge capacities because of their improved ability to suppress the surface-mediated reduction pathway. Furthermore, we find that redox mediation may be achieved with redox mediator reduction potentials significantly more positive than what has been explored, an insight which should help guide future redox mediator exploration.