Aqueous MnV2O6-Zn Battery with High Operating Voltage and Energy Density

Aqueous Zn ion batteries (AZIBs), featuring low cost, long-term cycling stability, and superior safety are promising for applications in advanced energy storage devices. However, they still suffer from unsatisfactory energy density and operating voltage, which are closely related to cathode materials used. Herein, the use of monoclinic MnV2O6 (MVO) is reported, which can be activated for high-capacity Zn ions storage by electrochemically oxidizing part of the Mn2+ to Mn3+ or Mn4+ while the remaining Mn2+ ions act as binders/pillars to hold the layer structure of MVO and maintain its integrity during charging/discharging process. Moreover, after introducing carbon nanotubes (CNT), the MVO:CNT composite not only provides robust 3D Zn-ion diffusion channels but also shows enhanced structural integrity. As a result, a MVO:CNT cathode delivers a high midpoint voltage (1.38 V after 3000 cycles at 2 A g(-1)) and a high energy density of 597.9 W h kg(-1). Moreover, DFT analyses clearly illustrate stepwise Zn ion insertion into the MnV2O6 lattice(,) and ex-situ analyses results further verify the highly structural reversibility of the MnV2O6 cathode upon extended cycling, demonstrating the good potential of MnV2O6 for the establishment of viable aqueous Zn ion battery systems.

Automated summary

This study reports the use of MnV2O6 as a material for aqueous Zn ion batteries, showing excellent performance in high-capacity Zn ion storage, with improved structural integrity and high energy density after introducing carbon nanotubes. DFT analyses demonstrate the stepwise Zn ion insertion into the MnV2O6 lattice, and ex-situ analyses confirm the high structural reversibility of the MnV2O6 cathode during extended cycling, highlighting the great potential of MnV2O6 for viable aqueous Zn ion battery systems.