Unlocking the role of electrolyte concentration for Na-O2 batteries
Journal article, 2024

Na-O2 batteries have attracted great interest in recent years mainly due to their high energy density, in theory having prospects to outperform the commercialized lithium-ion batteries. In the quest for optimization, a recently explored approach is to use highly concentrated electrolytes (HCEs). The knowledge of molecular level of solvation as function of electrolyte concentration and its impact on Na-O2 battery performance is, however, still very limited. In this work, experimental and computational methods are used to characterize the cation solvation and when the emergence of anions into the cation first solvation shell occurs, which affects the de-solvation process and formation of discharge products. Furthermore, the solid electrolyte interphase (SEI) formed using HCEs demonstrates presence of anion fragments, with poorer protection of the Na metal anode. Moreover, the use of HCEs is also linked to lowered capacity, possibly due to a decrease in the size of the cubic-shaped discharge products as the electrolyte concentration increases, causing clogging of the pores of the air cathode. Thus, increasing the electrolyte salt concentration seems to have a detrimental effect on the cyclability of Na-O2 batteries. Instead, electrolytes with a lower than conventional salt concentration show the best performance, which highlights the importance of carefully tuning the cation solvation alongside overall physico-chemical properties to enhance battery performance.

Solid electrolyte interphase

Solvation structure

Na solvation and desolvation +

Na-O battery 2

Concentrated electrolyte

Na metal

Author

N. Ortiz-Vitoriano

Basque Foundation for Science (Ikerbasque)

Basque Research and Technology Alliance (BRTA)

I. Ruiz de Larramendi

University of the Basque Country (UPV/EHU)

Gustav Åvall

Chalmers, Physics, Materials Physics

Humboldt University of Berlin

R. Cid

Basque Research and Technology Alliance (BRTA)

M. Enterría

Basque Research and Technology Alliance (BRTA)

Patrik Johansson

Centre national de la recherche scientifique (CNRS)

Chalmers, Physics, Materials Physics

Roza Bouchal

Chalmers, Physics, Materials Physics

Energy Storage Materials

2405-8297 (eISSN)

Vol. 70 103501

Highly concentrated electrolytes

Swedish Energy Agency (39909-1), 2015-02-01 -- 2019-09-30.

Next Generation Batteries

Swedish Research Council (VR) (2021-00613), 2021-12-01 -- 2032-12-31.

Subject Categories

Materials Chemistry

Other Chemical Engineering

DOI

10.1016/j.ensm.2024.103501

More information

Latest update

6/19/2024