Topological Engineering Electrodes with Ultrafast Oxygen Transport for Super-Power Sodium-Oxygen Batteries.

Yuan, Ruoxin; Tan, Chuan; Zhang, Zhuojun; Zeng, Li; Kang, Wenbin; Liu, Jingfeng; Gao, Xiangwen; Tan, Peng et al. · Adv Mater · 2024

basic_science · Level V

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Abstract

Sodium-oxygen battery has attracted tremendous interest due to its extraordinary theoretical specific energy (1605 Wh kg<sup>-1</sup> <sub>NaO2</sub>) and appealing element abundance. However, definite mechanistic factors governing efficient oxygen diffusion and consumption inside electrolyte-flooded air cathodes remain elusive thus precluding a true gas diffusion electrode capable of high discharge current (i.e., several mA cm<sup>-2</sup>) and superior output power. Herein, 3D-printing technology is adopted to create gas channels with tailored channel size and structure to demystify the diffusion-limited oxygen delivery process. It is revealed that as the clogging discharging products increase, large channel size, and interconnected channel structure are essential to guaranteeing fast O<sub>2</sub> diffusion. Moreover, to further encourage O<sub>2</sub> diffusion, a bio-inspired breathable cathode with progressively branching channels that balances between O<sub>2</sub> passage and reaction is 3D printed. This elaborated 3D electrode allows a sodium-oxygen cell to deliver an impressive discharging current density of up to 4 mA cm<sup>-2</sup> and an output power of 8.4 mW cm<sup>-2</sup>, giving rise to an outstanding capacity of 18.4 mAh cm<sup>-2</sup>. The unraveled mystery of oxygen delivery enabled by 3D printing points to a valuable roadmap for the rational design of metal-air batteries toward practical applications.