Katherine L. Van Aken
Drexel University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Katherine L. Van Aken.
Advanced Materials | 2015
Meng-Qiang Zhao; Chang E. Ren; Zheng Ling; Maria R. Lukatskaya; Chuanfang Zhang; Katherine L. Van Aken; Michel W. Barsoum; Yury Gogotsi
Free-standing and flexible sandwich-like MXene/carbon nanotube (CNT) paper, composed of alternating MXene and CNT layers, is fabricated using a simple filtration method. These sandwich-like papers exhibit high volumetric capacitances, good rate performances, and excellent cycling stability when employed as electrodes in supercapacitors.
Angewandte Chemie | 2015
Katherine L. Van Aken; Majid Beidaghi; Yury Gogotsi
An effective method to expand the operating potential window (OPW) of electrochemical capacitors based on formulating the ionic-liquid (IL) electrolytes is reported. Using model electrochemical cells based on two identical onion-like carbon (OLC) electrodes and two different IL electrolytes and their mixtures, it was shown that the asymmetric behavior of the electrolyte cation and anion toward the two electrodes limits the OPW of the cell and therefore its energy density. Also, a general solution to this problem is proposed by formulating the IL electrolyte mixtures to balance the capacitance of electrodes in a symmetric supercapacitor.
ACS Nano | 2016
Xiahan Sang; Yu Xie; Ming-Wei Lin; Mohamed Alhabeb; Katherine L. Van Aken; Yury Gogotsi; Paul R. C. Kent; Kai Xiao; Raymond R. Unocic
The 2D transition metal carbides or nitrides, or MXenes, are emerging as a group of materials showing great promise in lithium ion batteries and supercapacitors. Until now, characterization and properties of single-layer MXenes have been scarcely reported. Here, using scanning transmission electron microscopy, we determined the atomic structure of freestanding monolayer Ti3C2Tx flakes prepared via the minimally intensive layer delamination method and characterized different point defects that are prevalent in the monolayer flakes. We determine that the Ti vacancy concentration can be controlled by the etchant concentration during preparation. Density function theory-based calculations confirm the defect structures and predict that the defects can influence the surface morphology and termination groups, but do not strongly influence the metallic conductivity. Using devices fabricated from single- and few-layer Ti3C2Tx MXene flakes, the effect of the number of layers in the flake on conductivity has been demonstrated.
Journal of Physics: Condensed Matter | 2014
Katherine L. Van Aken; John K. McDonough; Song Li; Guang Feng; Suresh M. Chathoth; Eugene Mamontov; Pasquale F. Fulvio; Peter T. Cummings; Sheng Dai; Yury Gogotsi
While most supercapacitors are limited in their performance by the stability of the electrolyte, using neat ionic liquids (ILs) as the electrolyte can expand the voltage window and temperature range of operation. In this study, ILs with bis(trifluoromethylsulfonyl)imide (Tf2N) as the anion were investigated as the electrolyte in onion-like carbon-based electrochemical capacitors. To probe the influence of cations on the electrochemical performance of supercapacitors, three different cations were used: 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium and 1,6-bis(3-methylimidazolium-1-yl). A series of electrochemical characterization tests was performed using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS). Diffusion coefficients were measured using EIS and correlated with quasielastic neutron scattering and molecular dynamics simulation. These three techniques were used in parallel to confirm a consistent trend between the three ILs. It was found that the IL with the smaller sized cation had a larger diffusion coefficient, leading to a higher capacitance at faster charge-discharge rates. Furthermore, the IL electrolyte performance was correlated with increasing temperature, which limited the voltage stability window and led to the formation of a solid electrolyte interphase on the carbon electrode surface, evident in both the CV and EIS experiments.
Journal of the American Chemical Society | 2017
Xuehang Wang; Aleksandar Y. Mehandzhiyski; Bjørnar Arstad; Katherine L. Van Aken; Tyler S. Mathis; Alejandro Gallegos; Ziqi Tian; Dingding Ren; Edel Sheridan; Brian A. Grimes; De-en Jiang; Jianzhong Wu; Yury Gogotsi; De Chen
Ion-ion interactions in supercapacitor (SC) electrolytes are considered to have significant influence over the charging process and therefore the overall performance of the SC system. Current strategies used to weaken ionic interactions can enhance the power of SCs, but consequently, the energy density will decrease due to the increased distance between adjacent electrolyte ions at the electrode surface. Herein, we report on the simultaneous enhancement of the power and energy densities of a SC using an ionic mixture electrolyte with different types of ionic interactions. Two types of cations with stronger ionic interactions can be packed in a denser arrangement in mesopores to increase the capacitance, whereas only cations with weaker ionic interactions are allowed to enter micropores without sacrificing the power density. This unique selective charging behavior in different confined porous structure was investigated by solid-state nuclear magnetic resonance experiments and further confirmed theoretically by both density functional theory and molecular dynamics simulations. Our results offer a distinct insight into pairing ionic mixture electrolytes with materials with confined porous characteristics and further propose that it is possible to control the charging process resulting in comprehensive enhancements in SC performance.
Journal of Physical Chemistry Letters | 2017
Naresh C. Osti; Katherine L. Van Aken; Matthew W. Thompson; Felix Tiet; De-en Jiang; Peter T. Cummings; Yury Gogotsi; Eugene Mamontov
We explore the influence of the solvent dipole moment on cation-anion interactions and transport in 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl), [BMIM+][Tf2N-]. Free energy profiles derived from atomistic molecular dynamics (MD) simulations show a correlation of the cation-anion separation and the equilibrium depth of the potential of mean force with the dipole moment of the solvent. Correlations of the ion diffusivity with the dipole moment and the concentration of the solvent were further demonstrated by classical MD simulations. Quasi-elastic neutron scattering experiments with deuterated solvents reveal a complex picture of nanophase separation into the ionic liquid-rich and solvent-rich phases. The experiment corroborates the trend of concentration- and dipole moment-dependent enhancement of ion mobility by the solvent, as suggested by the simulations. Despite the considerable structural complexity of ionic liquid-solvent mixtures, we can rationalize and generalize the trends governing ionic transport in these complex electrolytes.
Advanced Energy Materials | 2016
Xiuqiang Xie; Taron Makaryan; Meng-Qiang Zhao; Katherine L. Van Aken; Yury Gogotsi; Guoxiu Wang
Journal of Power Sources | 2016
Ayeong Byeon; Alexey M. Glushenkov; Babak Anasori; Patrick Urbankowski; Jingwen Li; Bryan W. Byles; Brian Blake; Katherine L. Van Aken; Sankalp Kota; Ekaterina Pomerantseva; Jae W. Lee; Ying Chen; Yury Gogotsi
Journal of Power Sources | 2016
Zifeng Lin; Daffos Barbara; Pierre-Louis Taberna; Katherine L. Van Aken; Babak Anasori; Yury Gogotsi; Patrice Simon
Journal of Physical Chemistry C | 2014
Song Li; Katherine L. Van Aken; John K. McDonough; Guang Feng; Yury Gogotsi; Peter T. Cummings