Aqueous MnV₂ O₆ -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 MnV₂ O₆ (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 MnV₂ O₆ lattice_, and ex-situ analyses results further verify the highly structural reversibility of the MnV₂ O₆ cathode upon extended cycling, demonstrating the good potential of MnV₂ O₆ for the establishment of viable aqueous Zn ion battery systems.