Abstract
Li primary batteries have been used in commercial and military applications for decades due to their unrivaled energy density and long shelf-life. For years, the impressive shelf-life of these batteries has been primarily attributed to a stable solid electrolyte interphase (SEI), which hinders parasitic reactions at the anode/electrolyte interface. However, few published studies have probed electrode/electrolyte composition in commercial cells, and no previous studies have isolated contributions of the cathode and the electrolyte to SEI stability. To fill this knowledge gap, the present study attempts to de-convolute contributions from each entity by determining component compositions and unveiling the effect each constituent has on SEI stability. In this study, we investigate SEI compositions of three common Li primary chemistries - Li/MnO2, Li/FeS2 and Li/CFx, all of which display exceptional shelf-life. Additionally, due to the dynamic nature of the SEI, cells exposed to varying extents of ageing have been investigated to understand how the SEIs physical and chemical characteristics vary with time. Techniques such as X-ray Photoelectron Spectroscopy (XPS) and Energy-Dispersive Spectroscopy (EDS) are used to conduct chemical analysis of the SEI, while Scanning Electron Microscopy (SEM) is used to elucidate morphological changes in anode and SEI behavior as a function of extent of ageing and cathode/electrolyte chemistry.
This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.