2 research outputs found
Determinants of the Surface Film during the Discharging Process in Lithium–Oxygen Batteries
Lithium–oxygen batteries have one of the highest
theoretical
capacities and specific energies, but several challenges remain. One
of them is premature death caused by a passivation layer with poor
conductivities (both electronic and ionic) on the electrode surface
during the discharge process. Once this thin layer forms on the surface
of the catalyst and substrate, the overpotential significantly increases
and causes early cell death. Therefore, understanding this thin layer
is crucial to achieving high specific energy lithium–oxygen
batteries. Herein, we quantitatively compared the ratio of lithium
carbonate to lithium peroxide during the discharge process in a flow
cell at different potentials. We found that the ratio rapidly increased
at low potential and high flow rates. The surface route led to significant
byproducts on the Au electrodes, and consequently, a 3 nm thick discharge
product film passivates the electrode surface in a flow cell
Electron Localization in Rationally Designed Pt<sub>1</sub>Pd Single-Atom Alloy Catalyst Enables High-Performance Li–O<sub>2</sub> Batteries
Li–O2 batteries (LOBs) are considered
as one
of the most promising energy storage devices due to their ultrahigh
theoretical energy density, yet they face the critical issues of sluggish
cathode redox kinetics during the discharge and charge processes.
Here we report a direct synthetic strategy to fabricate a single-atom
alloy catalyst in which single-atom Pt is precisely dispersed in ultrathin
Pd hexagonal nanoplates (Pt1Pd). The LOB with the Pt1Pd cathode demonstrates an ultralow overpotential of 0.69
V at 0.5 A g–1 and negligible activity loss over
600 h. Density functional theory calculations show that Pt1Pd can promote the activation of the O2/Li2O2 redox couple due to the electron localization caused
by the single Pt atom, thereby lowering the energy barriers for the
oxygen reduction and oxygen evolution reactions. Our strategy for
designing single-atom alloy cathodic catalysts can address the sluggish
oxygen redox kinetics in LOBs and other energy storage/conversion
devices