Replacement of Carbon with TiO2 Electrodes By Tuning Electronic Conductivity and Porosity for Stable Li-O2 Batteries

Although carbon is ubiquitously used as the basis of the cathode, its use in Li-O 2 battery is still problematic in that carbon decomposes on charge above 3 V vs. Li/Li + , and leads to electrolyte decomposition on both discharge and charge, rendering it unsuitable for aprotic Li-O 2 cells. Meanwhile, a pioneering work from Bruce et al ., [1] suggested that carbon be replaced with TiC which promoted reversible formation of Li 2 O 2 . By the way, it is open to debate that the stability of TiC originates from the TiO 2 at the surface, and TiO 2 itself can be an air cathode, provided that the electrical conductivity is guaranteed. For this reason, porous TiO 2 [2] with some deliberate oxygen vacancies [3] was synthesized so that the electrode exhibited large surface area with moderate electronic and ionic conductivity. The porous black electrode showed a stable cycle-life performance, and the polarization during the decomposition of Li 2 O 2 is greatly improved. Therefore, it is expected that the electronic conductivity- and porosity-tuned TiO 2 can be a suitable substrate for Li-O 2 chemistry. Finally, the origin of high stability of this porous black TiO 2 as an air cathode is also investigated. [1] M. M. Ottakam Thotiyl, S. A. Freunberger, Z. Peng, Y. Chen, Z. Liu, and P.G.Bruce, Nat. Mater . 12 , 1050 (2013). [2] J.-H. Shin, J.-H. Kang, W.-M. Jin, J. H. Park, Y.-S. Cho, and J. H. Moon, Langmuir , 27 , 85 (2011). [3] X. Chen, L. Liu, and F. Huang, Chem. Soc. Rev . 44 , 1861 (2015).