Vanadium dissolution restraint and conductive assistant in MnV12O31·10H2O to boost energy storage property for aqueous zinc-ion batteries

Abstract

Hydrated vanadates have gained significant attentions as cathode ingredients for aqueous zinc-ion batteries (AZIBs) on account of their broad open channels in the structural framework together with the existence of crystal water for stabilizing the structure. Yet, the ambiguous zinc storage mechanism and sluggish electrochemical reaction dynamics are always challenging questions for the development of hydrated vanadate cathodes. Herein, a novel hydrated manganese vanadate MnV12O31·10H2O (MVOH) nanobelt assembled microparticle materials is synthesized and combined with carbon nanofibers (CNFs) to generate MVOH-CNFs composite through electrostatic attraction in the condition of hydrothermal environment. The zinc storage mechanism of the formed MVOH substance as a cathode for AZIBs is clarified by a combined in- and ex-situ characterizations. The advantages of the crystal structure of MVOH to restrain vanadium dissolution and the assistance of CNFs to meliorate reaction kinetics are clarified based on the density functional theory calculations. The MVOH-CNFs cathode with a CNF content of 10.1% exhibits a reversible capacity of 302 mAh g−1 at 2 A g−1 after 100 cycles and 105 mAh g−1 at 8 A g−1 after 5000 cycles with robust structural stability. It also delivers excellent areal and volumetric capacity especially at high current density. A quasi-solid MVOH-CNFs//Zn pouch battery based on a gel electrolyte exhibits stable electrochemical performance and could be curled into a circular shape on the wrist to power a smart watch. This work paves a way for the furtherance of hydrated manganese vanadate cathodes in the application of high performance AZIBs.