title: Optical Characterization of Commercial Lithiated Graphite Battery Electrodes and in Situ Fiber Optic Evanescent Wave Spectroscopy.
abstract: Optical characterization of graphite anodes in lithium ion batteries (LIB) is presented here for potential use in estimating their state of charge (SOC). The characterization is based on reflectance spectroscopy of the anode of commercial LIB cells and in situ optical measurements using an embedded optical fiber sensor. The optical characterization of the anode using wavelengths ranging from 500 to 900 nm supports the dominance of graphite over the solid electrolyte interface in governing the anode's reflectance properties. It is demonstrated that lithiated graphite's reflectance has a significant change in the near-infrared band, 750-900 nm, compared with the visible spectrum as a function of SOC. An embedded optical sensor is used to measure the transmittance of graphite anode in the near-infrared band, and the results suggest that a unique inexpensive method may be developed to estimate the SOC of a LIB.
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: AbdulRahman
authors.initials: A
authors.lastname: Ghannoum
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Norris
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Krishna
authors.initials: K
authors.lastname: Iyer
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Liliana
authors.initials: L
authors.lastname: Zdravkova
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Aiping
authors.initials: A
authors.lastname: Yu
authors.affiliation: Department of Chemical Engineering and ‡Department of Mechanical and Mechatronics Engineering, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Patricia
authors.initials: P
authors.lastname: Nieva
keywords: graphite; lithium ion batteries; optical fiber; reflectance; state of charge