TY - JOUR
T1 - The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li–O2 batteries
AU - Johnson, Lee
AU - Li, Chunmei
AU - Chen, Yuhui
AU - Liu, Zheng
AU - Freunberger, Stefan
AU - Tarascon, Jean-Marie
AU - Ashok, Praveen C.
AU - Praveen, Bavishna B.
AU - Dholakia, Kishan
AU - Bruce, Peter G.
PY - 2014
Y1 - 2014
N2 - When lithium–oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 reduction across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 reduction through its effect on the solubility of LiO2, or, more precisely, the free energy of the reaction LiO2* ⇌ Li(sol)+ + O2−(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-number solvents are likely to lead to premature cell death, and that the future direction of research for lithium–oxygen batteries should focus on the search for new, stable, high-donor-number electrolytes, because they can support higher capacities and can better sustain discharge.
AB - When lithium–oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 reduction across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 reduction through its effect on the solubility of LiO2, or, more precisely, the free energy of the reaction LiO2* ⇌ Li(sol)+ + O2−(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-number solvents are likely to lead to premature cell death, and that the future direction of research for lithium–oxygen batteries should focus on the search for new, stable, high-donor-number electrolytes, because they can support higher capacities and can better sustain discharge.
UR - http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2101.html
UR - http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2101.html
U2 - 10.1038/nchem.2101
DO - 10.1038/nchem.2101
M3 - Article
SN - 1755-4349
VL - 6
SP - 1091
EP - 1099
JO - Nature Chemistry
JF - Nature Chemistry
IS - 12
ER -