Extraordinary pseudocapacitive energy storage triggered by phase transformation in hierarchical vanadium oxides

Abstract

Pseudocapacitance holds great promise for improving energy densities of electrochemical supercapacitors, but state-of-the-art pseudocapacitive materials show capacitances far below their theoretical values and deliver much lower levels of electrical power than carbon-based materials due to poor cation accessibility and/or long-range electron transferability. Here we show that in situ corundum-to-rutile phase transformation in electron-correlated vanadium sesquioxide can yield nonstoichiometric rutile vanadium dioxide layers that are composed of highly sodium ion accessible oxygen-deficiency quasi-hexagonal tunnels sandwiched between conductive rutile slabs. This unique structure serves to boost redox and intercalation kinetics for extraordinary pseudocapacitive energy storage in hierarchical isomeric vanadium oxides, leading to a high specific capacitance of ~1856 F g–1 (almost sixfold that of the pristine vanadium sesquioxide and dioxide) and a bipolar charge/discharge capability at ultrafast rates in aqueous electrolyte. Symmetric wide voltage window pseudocapacitors of vanadium oxides deliver a power density of ~280 W cm–3 together with an exceptionally high volumetric energy density of ~110 mWh cm–3 as well as long-term cycling stability.

Surface Engineering for Advanced Aqueous Supercapacitors: A Review

“…Specifically, different from the interfacial restriction in composites, the heterostructure engineers the charge transfer across the interface. Jiang et al . designed a unique heterostructure, vacancy ordered rutile VO 2‐x phases (r‐VO 2‐x ) on corundum V 2 O 3 (c‐V 2 O 3 ) core (as shown in Figure a–b; denoted as NP c‐V 2 O 3 /r‐VO 2‐x ), to facilitate redox and intercalation kinetics for large energy storage at high rate.…”

Oxygen‐Deficient Homo‐Interface toward Exciting Boost of Pseudocapacitance

“…The energy density of SCs based on double‐layer capacitance, however, is very low as compared with that of batteries 5–7. In recent years, the development of pseudocapacitive materials that enable redox reactions at or near the material surface brings the hope to increase the energy density of SCs to the battery level 8–12. However, most of the pseudocapacitive materials (such as MnO 2 , SnO 2 , and Fe 2 O 3 ) possess sluggish ion diffusion and electron transport, which result in low bulk utilization for charge storage and limited gain in energy density for these pseudocapacitors 9,13,14.…”

“…In recent years, the development of pseudocapacitive materials that enable redox reactions at or near the material surface brings the hope to increase the energy density of SCs to the battery level 8–12. However, most of the pseudocapacitive materials (such as MnO 2 , SnO 2 , and Fe 2 O 3 ) possess sluggish ion diffusion and electron transport, which result in low bulk utilization for charge storage and limited gain in energy density for these pseudocapacitors 9,13,14. Therefore, it is still a topical challenge for pseudocapacitors to boost the quick‐response charge storage sites beyond the electrode–electrolyte interface.…”

Commercial-Level Energy Storage via Free-Standing Stacking Electrodes

“…Pseudocapacitors with fast faradic redox reactions during the electrochemical charge/ discharge process hold great promise to extend the charge storage levels compared with electrochemical double-layer capacitors (EDLCs), [1][2][3][4][5][6][7][8] potentially delivering high-power and high-energy densities to meet the fast-growing demands of portable electronic devices and hybrid vehicles. [9][10][11][12] Since the discovery of surface redox pseudocapacitance at the RuO 2 /aqueous electrolyte (H + ) interface, 13 faster intercalation pseudocapacitance in Nb 2 O 5 /organic electrolytes (Li + ), 14,15 LaMnO 3Gd /aqueous electrolytes (OH À ), 16 Ti 3 C 2 MXene/aqueous electrolytes (H + ), [17][18][19] and c-V 2 O 3 /r-VO 2Àx hybrid/aqueous electrolytes (Na + ) 20 have also been successfully developed to improve capacity and rate performances, while saving the charging time of metal oxides (carbides or nitrides)-based energy-storage devices. However, the state-of-the-art metal oxide-based pseudocapacitance materials still face challenges such as low electronic conductivity, slow ion transport in the atomic layer channels, and poor accessibility and wettability of electrolytes to active sites due to low surface area and pore structure limitations, making the capacitances remain far below their theoretical values and making it difficult to realize energy storage with battery-like capacity and carbon-based supercapacitor-like rate performances.…”