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The Effect of Crystallinity on the Rapid Pseudocapacitive Response of Nb 2 O 5
Author(s) -
Kim Jong Woung,
Augustyn Veronica,
Dunn Bruce
Publication year - 2012
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201100494
Subject(s) - pseudocapacitor , materials science , orthorhombic crystal system , capacitance , energy storage , faraday efficiency , pseudocapacitance , crystallinity , electrolyte , amorphous solid , supercapacitor , electrochemistry , capacitive sensing , phase (matter) , nanotechnology , chemical engineering , chemical physics , thermodynamics , electrode , crystallography , crystal structure , chemistry , power (physics) , electrical engineering , physics , composite material , engineering , organic chemistry
Capacitive energy storage offers several attractive properties compared to batteries, including higher power, faster charging, and a longer cycle life. A key limitation to this electrochemical energy‐storage approach is its low energy density and, for this reason, there is considerable interest in identifying pseudocapacitor materials where faradaic reactions are used to achieve greater charge storage. This paper reports on the electrochemical properties of Nb 2 O 5 and establishes that crystalline phases of the material undergo fast faradaic reactions that lead to high specific capacitance in short charging times. In particular, the specific capacitance for the orthorhombic phase at infinite sweep rate reaches ≈400 F g −1 , which exceeds that of birnessite MnO 2 in nonaqueous electrolyte and is comparable to RuO 2 at the same extrapolated rate. The specific capacitances of the orthorhombic and pseudohexagonal phases are much greater than that of the amorphous phase, suggesting that the faradaic reactions which lead to additional capacitive energy storage are associated with Li + insertion along preferred crystallographic pathways. The ability for Nb 2 O 5 to store charge at high rates despite its wide bandgap and low electronic conductivity is very different from what is observed with other transition metal oxides.