(212e) Impact of Cathode/Solvent Interfaces on the Electrochemical Performance of Na-O2 Batteries.

Aprotic Na-O₂ batteries have recently gained significant attention as promising alternatives to commercial Li-ion batteries owing to their high energy densities and reversible redox chemistries^1–3. The underlying electrochemistry in these systems is heavily influenced by the glyme-ether electrolyte solvents owing to their solvation properties that vary as a function of their respective chain lengths⁴. Na-O₂ systems with short chain ether electrolyte solvents are challenged by their long-term stability⁵ whereas, the systems with long chain ether electrolyte solvents lack fundamental understanding in their underlying electrochemistry¹. These challenges hamper the development of effective strategies to improve their stability and overall electrochemical efficiency³. Herein, we investigate the effect of the cathode/aprotic electrolyte solvent interface on the mechanism of discharge product formation and overall electrochemical cell performance by varying both the glyme-ether electrolyte solvent and the carbon electrode. Theoretical calculations are coupled with experimental X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) studies to determine the nature of the Na-O₂ species formed as a function of the electrolyte solvent and carbon cathode. A link between the nature of the carbon cathode/aprotic solvent interface, discharge mechanism for product formation and the overall electrochemical performance and stability is reported. These insights are critical for the rational design of efficient and stable Na-O₂ batteries.

References:

(1) Samira, S., et al., ACS Energy Lett, 2021, 6 (2), 665–674.

(2) Hartmann, P., et al., Nat. Mater. 2013, 12 (3), 228–232.

(3) Bi, X., et.al., Small Methods, 2019, 3 (4), 1800247.

(4) Lutz, L., et.al., The Journal of Physical Chemistry C, 2016, 120 (36), 20068–20076.

(5) Kim, J., et.al., Nat Commun, 2016, 7 (1), 10670.