Large Molecule Decomposition Products of Electrolytes and Additives Revealed by On-Electrode Chromatography and MALDI

Abstract

The solid-electrolyte interphase (SEI) produced by the decomposition of electrolyte has critical impact on battery performance. However, the precise makeup of SEI including the composition of organic species is one of the least understood aspects of lithium-ion batteries. Here, we probe the SEIs using Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry (MALDI-TOF-MS) assisted by on-electrode chromatography. MALDI is suitable for characterization of organic and polymer molecules but is inconvenient to couple with chromatography methods. This study employs on-electrode chromatography which utilizes the electrode itself as stationary phase for fractionating the molecules on the electrode surfaces, successfully introducing chromatography separation approaches for MALDI. With on-electrode chromatography, SEI components were characterized by MALDI directly on the electrodes. Large molecule decomposition products of carbonate electrolytes containing vinylene carbonate and methacrylate additives are unambiguously illustrated. This work provides a simple, powerful and universal solution for identification of the organic components in SEIs.