Oral Presentation Royal Australian Chemical Institute National Congress 2026

Discharging and Charging Redox Mediation in Li-O2 Electrolyte Design (138469)

Josh J Brown 1
  1. CSIRO, Canberra, ACT, Australia

Lithium-oxygen (Li-O2) batteries represent a promising next-generation energy storage technology due to their high theoretical energy density (~3500 Wh/kg, excluding oxygen mass).1 However, reaching the theoretical potential faces significant practical challenges in the realm of limited discharge capacity, large charging overpotentials, poor cycling stability and parasitic reactions induced by reactive oxygen species (ROS) that inhibit ORR/OER efficiency.2 Strategic design of liquid electrolyte compositions in these systems has emerged as a promising avenue for addressing these issues.3

Electrolyte composition can critically facilitate a solution route for formation of Li2O2 on discharge via solubilization of the LiO2 intermediate. ORR/OER efficiency is also intrinsically linked to suppression of parasitic side reactions and 1O2 formation.4

Redox mediators (RMs) have been investigated as soluble electrocatalysts to facilitate electron transfer during discharging and charging processes.1 RMs based on metal complexes while underexplored have the potential to facilitate bifunctional redox mediator and importantly O2 transport in the electrolyte via reversible O2 binding, superoxide stabilization and inner-sphere ORR.5 Based on analogous studies of ORR/OER complexes in aqueous solutions we have generated a screening dataset and protocol for the aprotic ORR/OER electrolyte Li-O2 based on the redox couples of Fe(II/III), Co(II/III), Ru(II/III) and V(IV/V).

Using a Density Functional Theory (DFT) protocol we screened redox mediator and electrolyte combinations (DMSO and TEGDME) in Li–O2 batteries across the three key molecular parameters of redox potential (E⁰), O2 transport on discharging and electron transfer rate (kET) on charging.

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