Potentiodynamics of the Zinc and Proton Storage in Disordered Sodium Vanadate for Aqueous Zn-Ion Batteries

Abstract

A rechargeable Zn-ion battery is a promising aqueous system, where coinsertion of Zn2+ and H+ could address the obstacles of the sluggish ionic transport in cathode materials imposed by multivalent battery chemistry. However, there is a lack of fundamental understanding of this dual-ion transport, especially the potentiodynamics of the storage process. Here, a quantitative analysis of Zn2+ and H+ transport in a disordered sodium vanadate (NaV3O8) cathode material has been reported. Collectively, synchrotron X-ray analysis shows that both Zn2+ and H+ storages follow an intercalation storage mechanism in NaV3O8 and proceed in a sequential manner, where intercalations of 0.26 Zn2+ followed by 0.24 H+ per vanadium atom occur during discharging, while reverse dynamics happens during charging. Such a unique and synergistic dual-ion sequential storage favors a high capacity (265 mA h g–1) and an energy density (221 W h kg–1) based on the NaV3O8 cathode and a great cycling life (a capacity retention of 78% after 2000 cycles) in Zn/NaV3O8 full cells.

Extended π-Conjugated System in Organic Cathode with Active C═N Bonds for Driving Aqueous Zinc-Ion Batteries

“…All of the above results indicate the reversible redox of DQP during a discharge/charge process with active CN bonds. Different from most of the reported organic materials with carbonyls as active sites for ZIBs, DQP delivers a relatively high initial capacity, owing to the more stable charged state with negative charge on N. As is known, proton insertion can be found in many ZIBs with inorganic − and organic cathodes. However, when it comes to organic cathodes with active CN bonds, the role of protons is still controversial. , Hence, clarifying the mechanism of proton storage is necessary for the following study.…”

Undesired Reactions in Aqueous Rechargeable Zinc Ion Batteries

“…All types of cathode materials, including V-, Mn-, and Co-based and Prussian blue analogs, undergo dissolution in aqueous electrolytes. ,,− There are three ways in which the cathode material can dissolve in the electrolyte. First, the cathode material can dissolve into the electrolyte while the battery is operational. ,− This dissolution has been ascribed to the fact that transition metal ions can become unstable during the charging/discharging step in the mildly acidic zinc electrolytes, and this has been discussed in detail in previous review papers. , …”

Aqueous zinc ion batteries based on sodium vanadate electrode materials with long lifespan and high energy density

“…Thereinto, it is important to further study vanadium-based cathodes because of their high capacity and rich oxidation states [23][24][25] . They mainly include: V 2 O 5 [26] , VO 2 [27] , and vanadates [28][29][30][31] , etc. However, their poor energy density and sluggish ion transfer speed have not been well resolved.…”