K2Ti6O13/carbon core-shell nanorods as a superior anode material for high-rate potassium-ion batteries.

The bunches of oriented K2Ti6O13 nanorods coated by thin carbon layer (4—7 nm) were prepared by combining hydrothermal and heating treatment in sequence, in which K2Ti6O13 nanorods possess long- and short-axis crystal orientations of and , respectively, contributing to a fast K+ diffusion, as well as the carbon coating layer improves the electron conductivity. In addition, the obtained K2Ti6O13/carbon has high compaction density beneficial to realize high volumetric specific capacity. When it was evaluated as potassium ion battery anode, it demonstrated a superior rate capability (122.5, 104.3, 92.3, 78.6 and 65.1 mAh g-1 at various current densities of 20, 50, 100, 200 and 500 mA g-1, respectively), favourable cycle life (118.5 mAh g-1 at 25 mA g-1 for 200 cycles) and high capacity retention.