Electrochemical reactivity mechanism of Ni3N with lithium

An attempt to extend the application of the electrochemical mechanism on nanosized transition metal in the range 1-5 nm to drive formation and decomposition of Li2O was made for other transition metal compounds. Using reactive pulsed laser deposition and dc discharge methods in a nitrogen ambient, a transition compound of Ni3N thin film has been fabricated successfully. The lithium electrochemical reaction of Ni3N thin-film electrode was first investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), the discharge and charge, cyclic voltammetry (CV), the in situ spectroelectrochemical measurements. An irreversible process in the lithium electrochemical reaction of Ni3N thin-film electrode was confirmed by spectroelectrochemical, CV, ex situ XRD, and XPS measurement. However, irreversible capacity loss between the first two cycles is only 5% of the first discharge. The observed diffraction peaks from metal nickel in the lithiated thin films showed good crystallinity with crystal size more than 5 nm confirmed by transmission electron microscopy (TEM) and selected area electron diffraction (SEAD). So the oxidation/reduction of nanosized metal may not be used for an explanation for the electrochemical behavior of Ni3N thin film. Another reaction mechanism involves rich transition metals dispersed into a lithium containing matrix, two kinds of roles of metallic nickel are revealed, one part of metallic nickel is nitrided and reduced in the lithium electrochemical reaction, another part of nickel seems to act as an active spectator to drive the formation and decomposition of Li3N. (C) 2004 The Electrochemical Society.