Brigitte Pecquenard

EPR identification of LixV2O5 phases generated by chemical and electrochemical lithium intercalation in V2O5

Abstract EPR of V IV species is used to identify the different Li x V 2 O 5 -phases (α, e, δ, γ) obtained by chemical intercalation of lithium in V 2 O 5 and to study the evolution of V 2 O 5 cathodes upon electrochemical lithium intercalation, which is characterized by two different behaviors depending on the composition range. For 0 x x > 1, the lack of reversibility arises from the γ-phase and free VO 2+ ions.

Nanoscale Chemical Characterization of Solid-State Microbattery Stacks by Means of Auger Spectroscopy and Ion-Milling Cross Section Preparation

The current sustained demand for smart and connected devices has created a need for more miniaturized power sources, hence for microbatteries. Lithium-ion or lithium-free all-solid-state thin-film batteries are adapted solutions to this issue. The capability to carry out spatially resolved chemical analysis is fundamental for the understanding of the operation in an all-solid-state microbattery. Classically cumbersome and not straightforward techniques as TEM/STEM/EELS and FIB preparation methods could be used to address this issue. The challenge in this work is to make the characterization of Li-based material possible by coupling ion-milling cross section preparation method and AES techniques to characterize the behavior of a LiCoO2 positive electrode in an all solid state microbattery. The surface chemistry of LiCoO2 has been studied before and after LiPON deposition. Modifications of the chemical environments characteristic of the positive electrode have been reported at different steps of the electrochemical process. An original qualitative and a semiquantitative analysis has been used in this work with the peak deconvolution method based on real, certified reference spectra to better understand the lithiation/delithiation process. This original coupling has demonstrated that a full study of the pristine, cycled, and post mortem positive electrode in a microbattery is also possible. The ion-milling preparation method allows access to a large area, and the resolution of Auger analysis is highly resolved in energy to separate the lithium and the cobalt signals in an accurate way.