Preparation and characterization of nanostructured Ni2N thin film as electrode for lithium ion storage

The hierarchical Ni2N thin films were fabricated by a method of reactive radio-frequency magnetron sputtering, operating at ambient temperature. The phase composition and microstructure of the Ni2N thin films were analyzed by using X-ray diffractometer, scanning electron microscopy and transmission electron microscopy (TEM). The Ni2N thin films were applied as electrodes for lithium ion storage with the metallic lithium as counter and reference electrode, and the related electrochemical characteristics were investigated. The binder-free Ni2N thin film electrodes show a reversible specific capacity of around 450 mA h g(-1) at a current density of 120 mA g(-1), and exhibit a superior rate performance with a specific capacity of 191.7 mA h g(-1) at a current density of 2240 mA g(-1). TEM analysis on the phase evolution of the (NiN)-N-2 thin film electrodes induced at various discharge/charge statuses revealed that the lithiation process has a stepwise mechanisms consisting of the Li+-intercalation reaction and a subsequent conversion reaction, while the delithiation process is mainly composed of a typical conversion reaction. (C) 2017 Elsevier B.V. All rights reserved.