Part I. Identification of large-molecule SEI components with on-electrode chromatography and MALDI techniques

Abstract: The solid-electrolyte interphase (SEI) is a key research topic for battery science, but the precise composition of SEIs is one of the least understood aspects of batteries, especially the makeup of organic and polymer elements. Here, we analyze SEIs using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) assisted by on-electrode chromatography. MALDI is a surface-compatible MS tool that is suitable for direct characterization of SEIs on electrode surfaces, and MALDI measurement of SEIs can be assisted by on-electrode chromatography that realizes controlled separation of different species on the electrodes, which proves critical for efficient MALDI characterization. In this study, the decomposition products of carbonate electrolyte and additives were identified directly on the electrode surfaces. This work demonstrates that MALDI is a convenient and universal approach for identification of organic SEI components.

Part II. Carbon coating prepared with polyvinylidene chloride (PVDC) precursor for silicon anodes applications

Abstract: A highly ordered carbon coating derived from polyvinylidene chloride (PVDC) precursor is developed for hosting silicon nanoparticles. The advantage of PVDC precursor is the stoichiometric ratio of sacrificial H and Cl elements that facilitates complete utilization of precursor's carbon content and thus formation of robust carbon coating. The optimal sintering temperature and carbon content have been investigated. It was found that Si:C 1:2 composite sintered at 800 °C provided excellent capacity retention as well as Coulombic efficiency, with a specific capacity of 709 mAh/g after 300 cycles at 0.3 C. This work demonstrates the benefit of polymer precursors with stoichiometric ratio of sacrificial elements for generating effective carbon coatings for silicon anodes.