Novel K2Ti8O17 Anode via Na+/Al3+ Co-Intercalation Mechanism for Rechargeable Aqueous Al-Ion Battery with Superior Rate Capability

A promising aqueous aluminum ion battery (AIB) was assembled using a novel layered K2Ti8O17 anode against an activated carbon coated on a Ti mesh cathode in an AlCl3-based aqueous electrolyte. The intercalation/deintercalation mechanism endowed the layered K2Ti8O17 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 indicated that the layered structure facilitated the intercalation/deintercalation of Na+/Al3+ ions, thus providing a high-rate performance of the K2Ti8O17 anode. The diffusion-controlled electrochemical characteristics and the reduction of Ti4+ species during the discharge process illustrated the intercalation/deintercalation mechanism of the K2Ti8O17 anode. This study provides not only insight into the charge-discharge mechanism of the K2Ti8O17 anode but also a novel strategy to design rechargeable aqueous AIBs.

Automated summary

This study demonstrated a promising aqueous aluminum ion battery utilizing a novel K2Ti8O17 anode, which exhibited excellent performance and cycling stability in the aqueous electrolyte. The introduction of NaAc enhanced the cycling stability of the battery, leading to high discharge voltage and capacity. Investigation using ICP-OES, HRTEM, and XANES revealed the intercalation/deintercalation mechanism of Na+/Al3+ ions in the aqueous AIB, providing insights into the charge-discharge mechanism of K2Ti8O17 anode.