Journal of Power Sources 160 (2006) 1381–1386 Structural, magnetic and electrochemical properties of lithium iron orthosilicate K. Zaghib a,∗ , A. Ait Salah b , N. Ravet c , A. Mauger b , F. Gendron b , C.M. Julien b a Institut de Recherche d’Hydro-Qu´ ebec (IREQ), 1200 Boulevard Boulet, Varennes, Que., Canada J3X 1S1 b Institut des Nano-Sciences de Paris, UMR-CNRS 7588, Universit´ e Pierre et Marie Curie, 140 rue de Lourmel 75015 Paris, France c D´ epartement de Chimie, Universit´ e de Montr´ eal, Montr´ eal, Que., Canada Received 1 February 2006; received in revised form 3 March 2006; accepted 6 March 2006 Available online 27 April 2006 Abstract We report the structural and electronic characterization of Li 2 FeSiO 4 synthesized by solid-state reaction. X-ray diffraction, Raman scattering, Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and magnetization measurements are ana- lyzed. Magnetic susceptibility experiments give evidence that Li 2 FeSiO 4 powders possess an antiferromagnetic ordering below T N = 25 K due to long range Fe–O–Li–O–Fe interactions. Analysis of the paramagnetic region giving the Curie–Weiss parameters θ p = -93.5 K and C p = 4.13 emu K mol -1 shows the divalent state of Fe cations. Electron paramagnetic resonance experiments confirm this electronic configuration. Electrochemical mea- surements were carried out in lithium cells with LiTFSI in a poly(ethylene oxide) (PEO) polymer electrolyte at 80 ◦ C. The resulting cyclic voltammogram indicates a stable structure for the first cycle with redox peaks at 2.80 and 2.74 V versus Li 0 /Li + . © 2006 Elsevier B.V. All rights reserved. Keywords: Lithium batteries; Orthosilicate; Magnetic properties; Optical spectroscopy 1. Introduction Since the demonstration of reversible lithium extrac- tion/insertion in frameworks built with (XO 4 ) n- polyanions (X = P, S, As, Mo) there is pressure for further development of advanced positive electrodes for rechargeable Li-ion batteries [1]. In particular, LiFePO 4 with an ordered olivine structure has been extensively investigated [2–4]. The use of polyanions such as (SiO 4 ) 4- in iron-based oxides could be advantageous because of the lower Fe 3+ /Fe 2+ redox. Orthosilicate Li 2 MSiO 4 materi- als, where M is a divalent transition metal (M = Fe, Mn, Co), are compounds related to the Li 3 PO 4 structure and are character- ized by a tetrahedral coordination of all cations. Tarte and Cahay [5] have shown that members of the orthosilicate and orthoger- manate groups have structures similar to the low-temperature ∗ Corresponding author. Tel.: +1 450 652 8019; fax: +1 450652 8424. E-mail address: karimz@ireq.ca (K. Zaghib). form of Li 3 PO 4 . The structure of Li 3 PO 4 has been accurately determined by Zemann who found that all cations (P and Li) are tetrahedrally coordinated [6]. Li 2 MSiO 4 compounds have been reported to crystallize in the orthorhombic system with a Pmn2 1 space group. Fig. 1 displays the crystal structure of Li 2 FeSiO 4 viewed along the b-axis. All the cations are tetrahedrally coor- dinated with oxygen atoms. As far as the iron orthosilicate is concerned, there are a few reports on the physico-chemical properties of this material. The structural and magnetic properties of Li 2 CoGeO 4 were investi- gated by Wintenberger [7]. An antiferromagnetic ordering was found below T N = 13.5 K due to long range Co–O–Li–O–Co interactions. Recently, Li 2 FeSiO 4 prepared by solid-state reac- tion has been proposed as a new positive electrode material for rechargeable Li-ion batteries [8]. In the present work, Li 2 FeSiO 4 is synthesized by solid- state reaction and characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Raman scattering (RS), Fourier transform infrared (FTIR) spectroscopy, SQUID 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.03.023