Novel k2 ti8 o17 anode via na+ /al3+ co-intercalation mechanism for rechargeable aqueous al-ion battery with superior rate capability

Abstract

A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2 Ti8 O17 anode against an activated carbon coated on a Ti mesh cathode in an AlCl3-based aqueous electrolyte. The intercalation/deintercalation mechanism endowed the layered K2 Ti8 O17 as a promising anode for rechargeable aqueous AIBs. NaAc was introduced into the AlCl3 aqueous electrolyte to enhance the cycling stability of the assembled aqueous AIB. The as-designed AIB displayed a high discharge voltage near 1.6 V, and a discharge capacity of up to 189.6 mAh g−1 . The assembled AIB lit up a commercial light-emitting diode (LED) lasting more than one hour. Inductively coupled plasma–optical emission spectroscopy (ICP-OES), high-resolution transmission electron microscopy (HRTEM), and X-ray absorption near-edge spectroscopy (XANES) were employed to investigate the intercalation/deintercalation mechanism of Na+ /Al3+ ions in the aqueous AIB. The results indi-cated that the layered structure facilitated the intercalation/deintercalation of Na+ /Al3+ ions, thus providing a high-rate performance of the K2 Ti8 O17 anode. The diffusion-controlled electrochemical characteristics and the reduction of Ti4+ species during the discharge process illustrated the intercala-tion/deintercalation mechanism of the K2 Ti8 O17 anode. This study provides not only insight into the charge–discharge mechanism of the K2 Ti8 O17 anode but also a novel strategy to design rechargeable aqueous AIBs.