The solid-electrolyte interphase (SEI) produced by decomposition of electrolyte is a key research topic for battery science because SEI has a critical impact on battery performance. However, the structure and composition of SEIs are the least understood aspects of batteries, partially due to the lack of electrode-specific characterization techniques, including the lack of analytical methods for precise determination of organic and organometallic species in SEIs. Here, we probe SEIs using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) assisted by on-electrode chromatography. MALDI is a classic MS tool for characterization of organic molecules, but it is difficult to couple MALDI with chromatography for separation of analytes and interferents. In this study, we carry out on-electrode chromatography for MALDI measurements, which utilizes the electrode itself as the stationary phase for fractionating the molecules on the electrode surface. With on-electrode chromatography, the decomposition products of electrolyte and additive were identified directly on the electrode surface. This study demonstrates that MALDI is suitable for identification of organic SEI components.