Tailoring Ultrahigh Energy Density and Stable Dendrite‐Free Flexible Anode with Ti₃C₂T_x MXene Nanosheets and Hydrated Ammonium Vanadate Nanobelts for Aqueous Rocking‐Chair Zinc Ion Batteries

Abstract

Exploiting Zn metal-free anode materials would be an effective strategy to resolve the problems of Zn metal dendrites that severely hinder the development of Zn ion batteries (ZIBs). However, the study of Zn metalfree anode materials is still in their infancy, and more importantly, the low energy density severely limits their practical implementations. Herein, a novel (NH 4 ) 2 V 10 O 25 • 8H 2 O@Ti 3 C 2 T x (NHVO@Ti 3 C 2 T x ) film anode is proposed and investigated for constructing "rocking-chair" ZIBs. The NHVO@Ti 3 C 2 T x electrode shows a capacity of 514.7 mAh g −1 and presents low potential which is 0.59 V (vs Zn 2+ /Zn) at 0.1 A g −1 . The introduction of Ti 3 C 2 T x not only affords an interconnected conductive network, but also stabilizes the NHVO nanobelts structure for a long cycle life (84.2% retention at 5.0 A g −1 over 6000 cycles). As a proof-of-concept, a zinc metal-free full battery is successfully demonstrated, which delivers the highest capacity of 131.7 mAh g −1 (mass containing anodic and cathodic) and energy density of 97.1 Wh kg −1 compared to all reported aqueous "rocking-chair" ZIBs. Furthermore, a long cycling span of 6000 cycles is obtained with capacity retention reaching up to 92.1%, which is impressive. This work is expected to provide new moment toward V-based materials for "rocking-chair" ZIBs.

Advances in the structure and composition design of zinc anodes for high performance zinc ion batteries

“…8f). Similar findings based on MXenes include V2C MXenea, 100 VSe 2 @V 2 CT x MXene nanohybrids, 96 NHVO@Ti 3 C 2 T x , 101 etc. The applications of MXenes are not limited to the anode or the current collector.…”

Potassium Ammonium Vanadate with Rich Oxygen Vacancies for Fast and Highly Stable Zn-Ion Storage

“…Compared to the pristine electrode, the intensity of V 5+ shows an apparent decrease and a new peak located at 515.4 eV is ascribed to V 3+ at the fully discharged state, which is associated with the reduction of V 5+ and V 4+ during the Zn 2+ intercalation process. 58,59 The contents of vanadium ions with different valence are inaccurate because trivalent vanadium ions are easily reduced during the ex situ XPS characterization. At the fully charged state, the V 4+ and V 3+ are reversibly oxidized to V 5+ .…”

Flexible Ti3C2Tx/Nanocellulose Hybrid Film as a Stable Zn-free Anode for Aqueous Hybrid Zn–Li Batteries

“…However, the working potential of intercalation-type electrode materials is often much larger than the redox potential of Zn 2+ /Zn in aqueous electrolytes, thereby decreasing the overall operating voltage of AZIBs. For example, Yuan et al utilized (NH 4 ) 2 V 10 O 25 ·8H 2 O as the anode material to replace zinc metals and realized improved cycling stability . Nevertheless, the average discharging voltage of AZIBs in that study is merely 0.6–0.7 V, which is too low for practical applications .…”