Structural and electrochemical properties of layered lithium nitridocuprates Li3-xCuxN

We report a systematic study of the layered lithium nitridocuprates Li3-xCuxN with 0.1 <= x <= 0.39. The structural data obtained from experimental XRD patterns, Rietveld refinements and unit cell parameters calculation vs x, indicate that copper (1) substitute interlayer lithium ions in the parent nitride Li3N to form the Li3-xCuxN compound without any Li vacancy in the Li2N- layer. Electrochemical results report Li insertion into the corresponding layered structures cannot take place in the 1.2/0.02 V voltage range as in the case of lithium into nitridonickelates and nitridocobaltates. However, in the initial charge process of Li3-xCuxN at 1.4 V leading to a specific capacity higher than 1000 mA h/g, the oxidation of copper and nitride ions is probably involved inducing a strong structural disordering process. As a consequence a new rechargeable electrochemical system characterized by discharge-charge potential of approximate to 0.3 V/1.2 V appears from the second cycle. Cycling experiments 0.02 V voltage/0.02 V range induce a complete destruction of the layered host lattice and the presence of Cu3N in the charge state suggests a conversion reaction. The capacity recovered in the 1.4/0.02 V range practically stabilizes around 500 mA h/g after 20 cycles. (C) 2008 Elsevier B.V. All rights reserved.