Boosting the Electrocatalytic Activity of Co 3 O 4 Nanosheets for a Li-O 2 Battery through Modulating Inner Oxygen Vacancy and Exterior Co 3+ /Co 2+ Ratio

作者：Junkai Wang, Rui Gao, Dong Zhou, Zhongjun Chen, Zhonghua Wu, G. Schumacher, Zhongbo Hu, Xiangfeng Liu · 发表于：ACS Catalysis · 年份：2017 · DOI：10.1021/acscatal.7b02313 · 被引用次数：315 · 研究领域：Advanced Battery Materials and Technologies、Advancements in Battery Materials、Advanced battery technologies research

Rechargeable Li-O 2 batteries have been considered as the most promising chemical power owing to their ultrahigh specific energy density. However, the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) result in high overpotential (∼1.5 V), poor rate capability, and even a short cycle life, which critically hinder their practical applications. Herein, we propose a synergistic strategy to boost the electrocatalytic activity of Co 3 O 4 nanosheets for Li-O 2 batteries by tuning the inner oxygen vacancies and the exterior Co 3+ /Co 2+ ratios, which have been identified by Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption near edge structure spectroscopy. Operando X-ray diffraction and ex situ scanning electron microscopy are used to probe the evolution of the discharge product. In comparison with bulk Co 3 O 4, the cells catalyzed by Co 3 O 4 nanosheets show a much higher initial capacity (∼24051.2 mAh g –1 ), better rate capability (8683.3 mAh g –1 @400 mA g –1 ) and cycling stability (150 cycles@400 mA g –1 ), and lower overpotential. The large enhancement in the electrochemical performances can be mainly attributed to the synergistic effect of the architectured 2D nanosheets, the oxygen vacancies, and Co 3+ /Co 2+ difference between the surface and the interior. Moreover, the addition of LiI to the electrolyte can further reduce the overpotential, making the battery more practical. This study offers some insights into designi...