High-Performance Na-O<sub>2</sub> Batteries Enabled by Oriented NaO<sub>2</sub> Nanowires as Discharge Products.

Khajehbashi, S Mohammad B; Xu, Lin; Zhang, Guobin; Tan, Shuangshuang; Zhao, Yan; Wang, Lai-Sen; Li, Jiantao; Luo, Wen et al. · Nano Lett · 2018

basic_science · Level V

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Abstract

Na-O<sub>2</sub> batteries are emerging rechargeable batteries due to their high theoretical energy density and abundant resources, but they suffer from sluggish kinetics due to the formation of large-size discharge products with cubic or irregular particle shapes. Here, we report the unique growth of discharge products of NaO<sub>2</sub> nanowires inside Na-O<sub>2</sub> batteries that significantly boosts the performance of Na-O<sub>2</sub> batteries. For this purpose, a high-spin Co<sub>3</sub>O<sub>4</sub> electrocatalyst was synthesized via the high-temperature oxidation of pure cobalt nanoparticles in an external magnetic field. The discharge products of NaO<sub>2</sub> nanowires are 10-20 nm in diameter and ∼10 μm in length, characteristics that provide facile pathways for electron and ion transfer. With these nanowires, Na-O<sub>2</sub> batteries have surpassed 400 cycles with a fixed capacity of 1000 mA h g<sup>-1</sup>, an ultra-low over-potential of ∼60 mV during charging, and near-zero over-potential during discharging. This strategy not only provides a unique way to control the morphology of discharge products to achieve high-performance Na-O<sub>2</sub> batteries but also opens up the opportunity to explore growing nanowires in novel conditions.