MeV-SIMS measurement of negative electrode surface of lithium ion battery after charging and discharging

The MeV-SIMS technique uses heavy ion beams with energies in the MeV range, allowing samples to be measured under ambient conditions due to the high transmission capability of these ions at low vacuum or atmospheric pressures. Ambient MeV-SIMS is a suitable method for investigating the reactions at the electrode–electrolyte interface. MeV-SIMS measurements were conducted on the LIB negative electrode after 1–20 charging and discharging cycles at 4.0 V. Numerous peaks are observed in the SIMS spectra of the negative electrode following charging and discharging, with most of these peaks originating from the surface of the LIB negative electrode. Some peak intensities increase or decrease depending on the number of charging and discharging cycles. The mass peaks whose intensity increased with charging and discharging cycles were predicted to be components remaining on the surface as the solid–electrolyte interphase (SEI), indicating that the SEI mainly contains organophosphate molecules.