Zinc pyrovanadate nanosheets of atomic thickness: excellent Li-storage properties and investigation of their electrochemical mechanism

Abstract

Exploring ternary metal oxides that can in situ form an elastic medium to accommodate volume changes upon lithium intercalation is now a popular and effective way to achieve high-performance lithium ion batteries with enhanced cycling stability. Herein, we report an ultrathin zinc pyrovanadate nanosheet of atomic thickness with exposed (001) facets via a facile hydrothermal method. Morphological and structural evolutions of the zinc pyrovanadate are investigated to reveal the electrochemical reaction mechanism of this compound towards lithium ion intercalations for the first time. It is found that the initial zinc pyrovanadate transforms into ZnO nanoparticles and LiV₂O₅ in the first cycle, and the subsequent reaction mainly occurs between ZnO and LiZn and lithiation/delithiation of the lithium vanadate. Interestingly, the in situ formed lithiated vanadate matrix could serve as a conductive network for the reversible electrochemical process of ZnO. The ultrathin thickness is in favour of shortening pathways for lithium ions, while the specific exposed facets are facilitated to form the architecture of ZnO nanoparticles embedded in the amorphous lithiated vanadate matrix owing to the sandwich-like skeleton of the zinc pyrovanadate that is constructed from the layer-by-layer stacking of the [ZnO₆] and [V₂O₇] polyhedra chains projected along the c axis. Benefiting from these inspiring merits, the as-synthesized ultrathin zinc pyrovanadate nanosheet exhibits a high specific capacity (963 mA h g⁻¹ at 0.05 A g⁻¹), outstanding rate capability (344 mA h g⁻¹ at 10 A g⁻¹), and long cycle life (602 mA h g⁻¹ could be maintained after 980 cycles at 1 A g⁻¹) and is regarded as a promising candidate for lithium ion battery anode materials.