At first, I -is oxidized to I2 at the carbon-electrolyte interface (Equation ). This reaction leads to solid I2 nanoparticles with a size limited by the electron tunneling/conduction thickness of the insulating I2 and the confining carbon cavities. Concurrently, I2 comproportionates to some extent with I -to I3 -(Equation ), with the amount of the latter growing with the amount of I2 (steadily increasing amounts of I3 -and I2, Fig. ). As I3 -and I2 amounts grow in the nanopores, the I5 -formation via the comproportionation (Equation ) accelerates.