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

Abstract

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.

Design Strategies for High‐Energy‐Density Aqueous Zinc Batteries

“…In recent years, some cathode materials (Mn‐ and V‐based materials) with both relatively high capacity and high voltage have been proposed, such as Co 0.247 V 2 O 5 ⋅0.944 H 2 O, [51] MnV 2 O 6 , [14b] and α‐MnO 2 [52] (see Table 3). However, they are still not ideal for ultrahigh‐energy‐density zinc batteries.…”

Hierarchical Carbon Nanosheet Embedded MnOx Cathode for High‐Performance Aqueous Zinc‐Ion Batteries

“…In this regard, it is speculated that the atomiclevel structure engineering can lead to changes in chemical and physical properties, which can improve the energy storage performance and cycling life as well. [36][37][38][39][40][41][42][43][44][45][46][47][48] However, designing MnO 2 cathodes at atomic-level scale with higher power and energy density still holds a huge challenge.…”

High‐Capacity and Long‐Life Manganese Vanadium Oxide Composite as a Cathode for Aqueous Zinc‐Ion Batteries

“…[37,38] A combination of Mn-and V-based oxides is an attractive choice for AZIBs for achieving superior cycling stability and high voltage. [39,40] Yan Wu et al reported the carbon nanotube (CNT)-wrapped MnV 2 O 6 as a cathode for AZ-IBs. The Mn 2+ could act as a pillar/binder to maintain the stable layer structure during the process.…”