Operando transmission electron microscopy of battery cycling: thickness dependent breaking of TiO₂ coating on Si/SiO₂ nanoparticles

Conformal coating of silicon (Si) anode particles is a common strategy for improving their mechanical integrity, to mitigate battery capacity fading due to particle volume expansion, which can result in particle crumbling due to lithiation induced strain and excessive solid-electrolyte interface formation. Here, we use operando transmission electron microscopy in an open cell to show that TiO2 coatings on Si/SiO2 particles undergo thickness dependent rupture on battery cycling where thicker coatings crumble more readily than thinner (∼5 nm) coatings, which corroborates the difference in their capacities.