cm403163c_si_001.pdf (3.1 MB)
First-Principles Study of the Reaction Mechanism in Sodium–Oxygen Batteries
journal contribution
posted on 2014-01-28, 00:00 authored by Byungju Lee, Dong-Hwa Seo, Hee-Dae Lim, Inchul Park, Kyu-Young Park, Jinsoo Kim, Kisuk KangLi/O2 battery has the
highest theoretical energy density
among any battery systems reported to date. However, its poor cycle
life and unacceptable energy efficiency from a high charging overpotential
have been major limitations. Recently, much higher energy efficiency
with low overpotential was reported for a new metal/oxygen system,
Na/O2 battery. This finding was unexpected since the general
battery mechanism of the Na/O2 system was assumed to be
analogous to that of the Li/O2 cell. Furthermore, it implies
that fundamentally different kinetics are at work in the two systems.
Here, we investigated the reaction mechanisms in the Na/O2 cell using first-principles calculations. In comparative study with
the Li/O2 cell, we constructed the phase stability maps
of the reaction products of Na/O2 and Li/O2 batteries
based on the oxygen partial pressure, which explained why certain
phases should be the main discharge products under different operating
conditions. From surface calculations of NaO2, Na2O2, and Li2O2 during the oxygen
evolution reaction, we also found that the minimum energy barrier
for the NaO2 decomposition was substantially lower than
that of Li2O2 decomposition on major surfaces
providing a hint for low charging overpotential of Na/O2 battery.