Dilimon V S, Hwang Chihyun, Cho Yoon-Gyo, Yang Juchan, Lim Hee-Dae, Kang Kisuk, Kang Seok Ju, Song Hyun-Kon
School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Korea.
Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, 08826, Korea.
Sci Rep. 2017 Dec 15;7(1):17635. doi: 10.1038/s41598-017-17745-9.
Stabilizing superoxide (O) is one of the key issues of sodium-air batteries because the superoxide-based discharge product (NaO) is more reversibly oxidized to oxygen when compared with peroxide (O) and oxide (O). Reversibly outstanding performances of sodium-oxygen batteries have been realized with the superoxide discharge product (NaO) even if sodium peroxide (NaO) have been also known as the discharge products. Here we report that the Lewis basicity of anions of sodium salts as well as solvent molecules, both quantitatively represented by donor numbers (DNs), determines the superoxide stability and resultantly the reversibility of sodium-oxygen batteries. A DN map of superoxide stability was presented as a selection guide of salt/solvent pair. Based on sodium triflate (CFSO)/dimethyl sulfoxide (DMSO) as a high-DN-pair electrolyte system, sodium ion oxygen batteries were constructed. Pre-sodiated antimony (Sb) was used as an anode during discharge instead of sodium metal because DMSO is reacted with the metal. The superoxide stability supported by the high DN anion/solvent pair ([Formula: see text] /DMSO) allowed more reversible operation of the sodium ion oxygen batteries.
稳定超氧化物（O）是钠-空气电池的关键问题之一，因为与过氧化物（O）和氧化物（O）相比，基于超氧化物的放电产物（NaO）被更可逆地氧化为氧气。即使过氧化钠（NaO）也被认为是放电产物，但基于超氧化物放电产物（NaO）的钠-氧电池已经实现了出色的可逆性能。在此我们报告，钠盐阴离子以及溶剂分子的路易斯碱度，均由给体数（DNs）定量表示，它决定了超氧化物的稳定性，进而决定了钠-氧电池的可逆性。给出了超氧化物稳定性的DN图作为盐/溶剂对的选择指南。基于三氟甲磺酸钠（CFSO）/二甲基亚砜（DMSO）作为高DN对电解质体系，构建了钠离子氧电池。放电过程中使用预钠化的锑（Sb）作为阳极而非金属钠，因为DMSO会与金属发生反应。由高DN阴离子/溶剂对（[化学式：见原文] /DMSO）支持的超氧化物稳定性使得钠离子氧电池能够实现更可逆的运行。
