Coupling Engineering of NH 4 + Pre-Intercalation and Rich Oxygen Vacancies in Tunnel WO 3 Toward Fast and Stable Rocking Chair Zinc-Ion Battery.

Herein, for the first time, a pre-intercalated non-metal ion (NH 4 + ) with rich oxygen vacancies stabilized tunnel WO 3 is proposed as a new intercalation anode to construct Zn-metal-free rocking-chair ZIBs. With the ethylene glycol additive in the aqueous electrolyte, the Zn 2+ solvation structure can be regulated and the side reaction of hydrogen evolution can also be suppressed. Owing to the integrated synergetic modification, a high-rate and ultra-stable aqueous Zn-(NH 4 ) x WO 3 battery can be constructed, which exhibits an improved specific capacity (153 mAh g -1 at 0.1 A g -1 ), excellent rate performance (when the current density increases to 3 A g -1 , the specific capacitance is still 86 mAh g -1 ), and a high cycle stability with 100% capacity retention after 2,200 cycles under 5 A g -1 . Ex situ X-ray diffraction and XPS reveal the reversible insertion/extraction of Zn 2+ in (NH 4 ) x WO 3 . The assembled (NH 4 ) x WO 3 //MnO 2 rocking-chair ZIBs delivers excellent capacity of 82 mAh g -1 at 0.1 A g -1 , impressive cyclic stability. Additionally, the flexible (NH 4 ) x WO 3 //MnO 2 ZIBs can power the electrochromic device-based PANI/WO 3 with high color contrast and fast response time. This study provides new insight for developing high-performance rechargeable aqueous ZIBs.