title: In Situ STEM-EELS Observation of Nanoscale Interfacial Phenomena in All-Solid-State Batteries.
abstract: Behaviors of functional interfaces are crucial factors in the performance and safety of energy storage and conversion devices. Indeed, solid electrode-solid electrolyte interfacial impedance is now considered the main limiting factor in all-solid-state batteries rather than low ionic conductivity of the solid electrolyte. Here, we present a new approach to conducting in situ scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) in order to uncover the unique interfacial phenomena related to lithium ion transport and its corresponding charge transfer. Our approach allowed quantitative spectroscopic characterization of a galvanostatically biased electrochemical system under in situ conditions. Using a LiCoO2/LiPON/Si thin film battery, an unexpected structurally disordered interfacial layer between LiCoO2 cathode and LiPON electrolyte was discovered to be inherent to this interface without cycling. During in situ charging, spectroscopic characterization revealed that this interfacial layer evolved to form highly oxidized Co ions species along with lithium oxide and lithium peroxide species. These findings suggest that the mechanism of interfacial impedance at the LiCoO2/LiPON interface is caused by chemical changes rather than space charge effects. Insights gained from this technique will shed light on important challenges of interfaces in all-solid-state energy storage and conversion systems and facilitate improved engineering of devices operated far from equilibrium.
authors.affiliation: Department of NanoEngineering, University of California , San Diego, La Jolla, California 92093, United States.
authors.forename: Ziying
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of NanoEngineering, University of California , San Diego, La Jolla, California 92093, United States.|Amrita Centre for Nanosciences and Molecular Medicine, Amrita Vishwa Vidyapeetham University , Kochi, Kerala 682041, India.
authors.forename: Dhamodaran
authors.initials: D
authors.lastname: Santhanagopalan
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Huolin L
authors.initials: HL
authors.lastname: Xin
authors.affiliation: Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: He
authors.affiliation: Material Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Juchuan
authors.initials: J
authors.lastname: Li
authors.affiliation: Material Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Nancy
authors.initials: N
authors.lastname: Dudney
authors.affiliation: Department of NanoEngineering, University of California , San Diego, La Jolla, California 92093, United States.
authors.forename: Ying Shirley
authors.initials: YS
authors.lastname: Meng
keywords: Lithium ion battery; in situ TEM; interfacial phenomena; solid electrolyte; thin film battery