A Highly Stable Sodium–Oxygen Battery Using a Mechanically Reinforced Membrane

Abstract

Sodium–oxygen batteries have drawn considerable attention due to their high specific energy and the high abundance of sodium. However, stable sodium–oxygen batteries currently require complex cathode formulations. Here, the first demonstration of a highly stable sodium–oxygen system comprising a simple carbon cathode, an ultradry electrolyte, and a newly designed separator that is both capable of blocking dendrites and is impenetrable to oxygen is reported. The battery shows remarkable rechargeability of more than 400 cycles at the current density of 0.28 mA m−2 to the capacity of 1.0 mAh cm−2. An oxygen diffusion study using a dye‐assisted visual chemical reaction proves that the separator efficiently restricts oxygen crossover toward the anode. An in situ atomic force microscope study shows that the discharge product (NaO2) is stable against the electrolyte under anhydrous conditions for over 48 h in either argon or oxygen atmospheres. The sodium–oxygen battery also demonstrates small overpotential (<40 mV) upon charging and remarkable oxygen efficiency (>96%).

Recent Development of Aprotic Na−O2 Batteries

“…The good mechanical strength of Nafion membranes efficiently suppress the dendrite penetration, and the cycle life is significantly improved to 120 cycles. Besides, a polypropylene‐TiO 2 ‐polypropylene (PP−TiO 2 −PP) sandwiched separator in Figure d, and mechanically reinforced glass microfiber frameworks with either aluminum oxide (to form α‐RGMF) or sodium beta‐alumina (to form β‐RGMF) particles are reported with a prolonged cycle life in Na−O 2 batteries.…”

“…Since room‐temperature aprotic Na−O 2 batteries were first reported in 2012, discharge products including NaO 2 , Na 2 O 2 , Na 2 O 2 ⋅ 2H 2 O, Na 2 CO 3 and NaOH have been identified under more or less similar experimental conditions. They are technologically and scientifically important to understand how these different products are formed, which will not only favor designing better Na−O 2 batteries but also provide profound understanding of aprotic metal‐air batteries.…”

In situ AFM visualization of Li–O2 battery discharge products during redox cycling in an atmospherically controlled sample cell

“…The main aim was to obtain electrochemical impedance spectroscopy (EIS), discharge/recharge voltages and capacities time-domain-correlated with AFM images of topography, all in a completely atmospherically isolated and controlled setting. In our recent study [30] using this in situ AFM set-up we monitored surface changes on the products of a Na–oxygen discharge reaction. The terms electrochemical cell and battery are used interchangeably in this study.…”

Bifunctional Effects of Cation Additive on Na‐O2Batteries

“…Many strategies towards dendrite suppression have been reported to extend the lifespan of aprotic Na‐O 2 batteries [10, 13] . Mechanically reinforced separators and hybrid solid state electrolyte were reported to physically block piercing by dendrites and enhance the cycling stability with additional battery construction [14, 15] . Alkali cations of Li + and K + were added to suppress Na dendrite formation through the electrostatic shielding effect [16–18] .…”

“…[10,13] Mechanically reinforced separators and hybrid solid state electrolyte were reported to physically block piercing by dendrites and enhance the cycling stability with additional battery construction. [14,15] Alkali cations of Li + and K + were added to suppress Na dendrite formation through the electrostatic shielding effect. [16][17][18] Nevertheless,the dominant discharge products of Li 2 O 2 and KO 2 are preferred instead of NaO 2 ,which will lead to sluggish oxygen reduction reactions at the cathode.O nt he other hand, the dissolved O 2 and O 2 À favor the Na dendrite formation, and the effects have rarely been considered, which are essential for the development of Na-O 2 batteries.…”