TY - JOUR
T1 - Electrochemical windows of room-temperature ionic liquids from molecular dynamics and density functional theory calculations
AU - Ong, Shyue Ping
AU - Andreussi, Oliviero
AU - Wu, Yabi
AU - Marzari, Nicola
AU - Ceder, Gerbrand
PY - 2011/6/14
Y1 - 2011/6/14
N2 - We investigated the cathodic and anodic limits of six room-temperature ionic liquids (ILs) formed from a combination of two common cations, 1-butyl-3-methylimidazolium (BMIM) and N,N-propylmethylpyrrolidinium (P13), and three common anions, PF6, BF4, and bis(trifluoromethylsulfonyl)imide (TFSI), using an approach that combines molecular dynamics (MD) simulations and density functional theory (DFT) calculations. All interion interactions were taken into account by explicitly modeling the entire liquid structure using classical MD, followed by DFT computations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The relative cathodic and anodic limits of BMIM PF6, BMIM BF4, BMIM TFSI, and P13 TFSI obtained from our approach are in fairly good agreement with existing experimental data. From our DFT calculations, we also obtained the cation- and anion-projected density of states (DOS), which provide information on the likely species contributing to reductive and oxidative decomposition. Our predictions support Howlett et al.'s earlier finding(1)that the TFSI anion is less stable than the P13 cation against reduction. In addition, our results provide surprising evidence of possible cation anodic instability; we predict the aromatic BMIM cation to be less stable against oxidation than the respective anions in BMIM PF6 and BMIM BF4, and the P13 cation to be less stable against oxidation than the PF6 anion in P13 PF 6. We also present a comparison of the predictions of our approach with that of simpler approximations based on in vacuo or polarizable continuum model calculations.
AB - We investigated the cathodic and anodic limits of six room-temperature ionic liquids (ILs) formed from a combination of two common cations, 1-butyl-3-methylimidazolium (BMIM) and N,N-propylmethylpyrrolidinium (P13), and three common anions, PF6, BF4, and bis(trifluoromethylsulfonyl)imide (TFSI), using an approach that combines molecular dynamics (MD) simulations and density functional theory (DFT) calculations. All interion interactions were taken into account by explicitly modeling the entire liquid structure using classical MD, followed by DFT computations of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The relative cathodic and anodic limits of BMIM PF6, BMIM BF4, BMIM TFSI, and P13 TFSI obtained from our approach are in fairly good agreement with existing experimental data. From our DFT calculations, we also obtained the cation- and anion-projected density of states (DOS), which provide information on the likely species contributing to reductive and oxidative decomposition. Our predictions support Howlett et al.'s earlier finding(1)that the TFSI anion is less stable than the P13 cation against reduction. In addition, our results provide surprising evidence of possible cation anodic instability; we predict the aromatic BMIM cation to be less stable against oxidation than the respective anions in BMIM PF6 and BMIM BF4, and the P13 cation to be less stable against oxidation than the PF6 anion in P13 PF 6. We also present a comparison of the predictions of our approach with that of simpler approximations based on in vacuo or polarizable continuum model calculations.
KW - bis(trifluoromethylsulfonyl)imide
KW - density functional theory
KW - Electrochemical windows
KW - imidazolium
KW - ionic liquids
KW - molecular dynamics
KW - polarizable continuum model
KW - pyrrolidinium
KW - room temperature
UR - http://www.scopus.com/inward/record.url?scp=84962360997&partnerID=8YFLogxK
U2 - 10.1021/cm200679y
DO - 10.1021/cm200679y
M3 - Article
AN - SCOPUS:84962360997
SN - 0897-4756
VL - 23
SP - 2979
EP - 2986
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 11
ER -