Atomic layer deposition of TiO2 on nitrogen-doped carbon nanofibers supported Ru nanoparticles for flexible Li-O2 battery: A combined DFT and experimental study

Flexible Li-O 2 batteries have attracted worldwide research interests and been considered to be potential alternatives for the next-generation flexible devices. Nitrogen-doped carbon nanofibers (N-CNFs) prepared by electrospinning are used as flexible substrate and an amorphous TiO 2 layer is coated by atomic layer deposition (ALD) and then decorated with Ru nanoparticles . The Ru/N-CNFs@TiO 2 composite is directly used as a free-standing electrode for Li-O 2 batteries and the electrode delivers a high specific capacity, improved round-trip efficiency and good cycling ability. The superior electrochemical performance can be attributed to the amorphous TiO 2 protecting layer and superior catalytic activity of Ru nanoparticles. Based on density functional theory (DFT) calculations from first principles, the carbon electrode after coating with TiO 2 is more stable during discharge/charge process. The analysis of Li 2 O 2 on three different interfaces (Li 2 O 2 /N-CNFs, Li 2 O 2 /TiO 2 , and Li 2 O 2 /Ru) indicates that the electron transport capacity was higher on Ru and TiO 2 compared with N-CNFs, therefore, Li 2 O 2 could be formed and decomposed more easily on the Ru/N-CNFs@TiO 2 cathode. This work paves a way to develop the free-standing cathode materials for the future development of high-performance flexible energy storage systems .