title: Conjugated polymer energy level shifts in lithium-ion battery electrolytes.
abstract: The ionization potentials (IPs) and electron affinities (EAs) of widely used conjugated polymers are evaluated by cyclic voltammetry (CV) in conventional electrochemical and lithium-ion battery media, and also by ultraviolet photoelectron spectroscopy (UPS) in vacuo. By comparing the data obtained in the different systems, it is found that the IPs of the conjugated polymer films determined by conventional CV (IPC) can be correlated with UPS-measured HOMO energy levels (EH,UPS) by the relationship EH,UPS = (1.14 ± 0.23) × qIPC + (4.62 ± 0.10) eV, where q is the electron charge. It is also found that the EAs of the conjugated polymer films measured via CV in conventional (EAC) and Li(+) battery (EAB) media can be linearly correlated by the relationship EAB = (1.07 ± 0.13) × EAC + (2.84 ± 0.22) V. The slopes and intercepts of these equations can be correlated with the dielectric constants of the polymer film environments and the redox potentials of the reference electrodes, as modified by the surrounding electrolyte, respectively.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Charles Kiseok
authors.initials: CK
authors.lastname: Song
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Eckstein
authors.forename: Teck Lip Dexter
authors.initials: TL
authors.lastname: Tam
authors.forename: Lynn
authors.initials: L
authors.lastname: Trahey
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks
keywords: conjugated polymer; cyclic voltammetry; electrolyte; electron affinity; lithium-ion battery; organic photovoltaics