How Dopants Can Enhance Charge Transport in Li₂O₂

The performance of high-capacity Li/O₂ batteries is limited by the high overpotential associated with the oxygen evolution reaction (OER) during charging. These losses have been attributed to sluggish charge transport within the solid lithium peroxide (Li₂O₂) discharge phase. Recent experiments have shown that use of Co₃O₄-containing Li/O₂ electrodes enhances rechargeability, but the mechanism responsible for this effect is unclear, as are the general prospects for the promotion of the Li/O₂ OER. Here first-principles calculations are combined with continuum-scale transport theory to build a multiscale model which demonstrates that the incorporation of trace Co into Li₂O₂ is a plausible mechanism for OER promotion. These calculations suggest that doping at equilibrium levels (tens of ppm) can enhance charge transport by shifting the balance of Li-ion vacancies and hole polarons. This mechanism could rationalize the improved rechargeability observed in Li/O₂ electrodes containing Co. On the basis of a computational assessment of 22 additional dopants, we speculate that Ni may also be an effective OER promoter