title: High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance.
abstract: Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2·xH2O in an acidic electrolyte. However, we recently demonstrated that a pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1,2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 μm thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices.
authors.affiliation: Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Augustyn
authors.forename: Jérémy
authors.initials: J
authors.lastname: Come
authors.forename: Michael A
authors.initials: MA
authors.lastname: Lowe
authors.forename: Jong Woung
authors.initials: JW
authors.lastname: Kim
authors.forename: Pierre-Louis
authors.initials: PL
authors.lastname: Taberna
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Tolbert
authors.forename: Héctor D
authors.initials: HD
authors.lastname: Abruña
authors.forename: Patrice
authors.initials: P
authors.lastname: Simon
authors.forename: Bruce
authors.initials: B
authors.lastname: Dunn
mesh_terms: D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods*; D004566:Electrodes; D007364:Intercalating Agents / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D009556:Niobium / Q000737:chemistry; D010087:Oxides / Q000737:chemistry
chemical_list: D007364:Intercalating Agents; D010087:Oxides; D009556:Niobium; D008094:Lithium; C073337:niobium pentoxide