A method for analyzing two-dimensional lithium ion concentration in the nano silicon films

With the variation of thickness and composition, the color of the nanosilicon film electrode in lithium ion batteries would be changed during lithium ion intercalation and deintercalation. Based on such phenomenon, here we present a method for evaluating the two-dimensional lithium ion concentration in the nanosilicon film. In the demonstration of a silicon film with thickness ∼115 nm, the correlation between tristimulus values and lithium ion concentration is established. In a piece of a large silicon film, the inhomogeneous lithium ion concentration could be obtained, highlighting a fast and noncontact method for in situ observation and analyses of the kinetic process of ion intercalation and deintercalation in nanosilicon films.