Lithium-ion batteries (LIBs) are reaching their theoretical energy limit, but still cannot meet the needs for all-electric vehicles. Owing to their five times higher energy density (~3500 W h/kg) than that of LIBs, lithium–air (Li–O₂) batteries have been considered as one of most promising next-generation energy storage devices.¹ However, Li–O₂ batteries still suffer from several challenges that hinder their practical applications, such as low energy efficiency and poor cycle life.² Recently, it has been demonstrated that the gradual accumulation of side products due to parasitic reactions can result in the failure of Li–O₂ batteries.³ Therefore, the cyclic performance of Li–O₂ batteries can be significantly improved by preventing the accumulation of side products.

Metal–organic frameworks (MOFs), a novel type of crystalline porous materials, have been widely studied as adsorbents for gas separation or storage due to their large surface area, high micro-porosity, and chemically unsaturated metal sites.⁴ Recently, MOFs-modified separators have been reported as molecular sieves to mitigate the shuttling effect of polysulfides in lithium–sulfur batteries.⁵ Herein, we report a MOFs-modified separator for Li–O₂ batteries. In this work, nanocrystalline MOFs are prepared and then coated on a GF/D separator by a facile method. The as-fabricated MOFs-modified separator showed much-improved cycle life up to 200 cycles at a current rate of 125 mA/g, compared to untreated GF/D separator. The mechanism of how MOFs mitigate the accumulation of side products on the cathode will be also discussed in this presentation.

Reference

1 Bruce, P. G., Freunberger, S. A., Hardwick, L. J. & Tarascon, J. M. Li–O₂ and Li–S batteries with high energy storage. Nat Mater 11, 19-29, doi:10.1038/nmat3191 (2012).

2 Luntz, A. C. & McCloskey, B. D. Nonaqueous Li–air batteries: a status report. Chem Rev 114, 11721-11750, doi:10.1021/cr500054y (2014).

3 Kim, B. G. et al. Ordered Mesoporous Titanium Nitride as a Promising Carbon-Free Cathode for Aprotic Lithium–Oxygen Batteries. ACS nano 11, 1736-1746 (2017).

4 Furukawa, H., Cordova, K. E., O’Keeffe, M. & Yaghi, O. M. The chemistry and applications of metal-organic frameworks. Science 341, 1230444 (2013).

5 Bai, S., Liu, X., Zhu, K., Wu, S. & Zhou, H. Metal–organic framework-based separator for lithium–sulfur batteries. Nat. Energy 1, 16094 (2016).