). A solution mechanism takes place in solvents with high donor number, where the superoxide ion forms ion pairs and higher aggregates with Li + ions in the solution, which diffuse before chemical disproportion into Li 2 O 2 , leading to the formation of a thick layer. Solvents with low donor number promote the surface mechanism, leading to thin films (< 10 nm in thickness) due to the insulating nature of the deposit that self limit its growth.