Available online at www.sciencedirect.com Journal of Power Sources 174 (2007) 501–507 FePO 4 nanoparticles supported on mesoporous SBA-15: Interesting cathode materials for Li-ion cells C. Gerbaldi a,∗ , G. Meligrana a , S. Bodoardo a , A. Tuel b , N. Penazzi a a Dipartimento di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, c.so Duca degli Abruzzi, 24, 10129 Torino (TO), Italy b Institut de Recherches sur la Catalyse, CNRS (UPR 5401) 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex, France Available online 30 June 2007 Abstract Exploiting the properties of stability, low cost and low toxicity of iron phosphates, we have tried to enhance the performance of FePO 4 as cathode material for Li-ion cells. We adopted the strategy of obtaining FePO 4 , via a typical preparation, onto the channels of an ordered mesoporous SBA-15 silica, a low cost mesoporous material commonly used in industry, which possesses larger pores, thicker walls and higher thermal stability as compared with other mesoporous silicas like MCM-41. Characterizations with ICP-AES, XRPD, BET and HRTEM suggest that the supported iron phosphate species, with loading amounts as high as 30 wt%, are located and dispersed in the mesopores of SBA-15. Iron phosphate can be reduced/oxidized more readily than the unsupported iron phosphate at room temperature, and in fact, cycling at C/10, the supported phosphate shows a utilization of 70% with respect to a value of 30% for the unsupported solid. The result is interesting from the scientific viewpoint but not suitable for application at the moment. Indeed, the amount of active material does not exceed 30% of the electrode mass and the total electrode capacity, though the active material is very efficient, is largely insufficient. Researches are being developed trying to increase the performances of the materials and also to eliminate the support after the dispersion of the active material. © 2007 Elsevier B.V. All rights reserved. Keywords: Li-ion batteries; Mesoporous; Iron(III) phosphate; Wet Impregnation; Electrochemical tests 1. Introduction Innovative fields of application for Li-ion batteries, like the electric vehicle (EV) technology, put in particular evidence the importance, for the electrode materials, of being ecologically friendly and low cost. Moreover, the cell voltage seems no longer of primary importance: high voltage is desirable, but it is in general related to the instability of the material and to possible problems with the electrolyte. High performance at ambient tem- perature is also not so important as one deals with temperatures of 60–80 ◦ C in EV applications. Recently, the whole of these considerations raised the interest for Fe(III) stable phosphates, particularly FePO 4 . Its Fe 3+ /Fe 2+ couple potential (about 3.0 V versus Li + /Li) is not so high to arise problems of stability of the system, and not so low to give an insufficient specific power. The theoretical capacity is ∗ Corresponding author. Tel.: +39 011 564 46 38; fax: +39 011 564 46 99. E-mail address: claudio.gerbaldi@polito.it (C. Gerbaldi). high: 178 mAh g -1 for the anhydrous form (for the well known phospho-olivine LiFePO 4 it is 170 mAh g -1 ), and 143 mAh g -1 for FePO 4 ·2H 2 O. Moreover, the synthesis of a Fe(III) com- pound, due to the Fe(III) stability, is less critical as compared to Fe(II) materials. Nevertheless, the behavior of FePO 4 cathode materials suffers from a difficult diffusion of Li + ions inside the structure and from a very low electronic conductivity. Thus, improvement of the electrochemical behavior has fol- lowed different lines in time. Most of researchers have focused their interest on the possible FePO 4 structures (crystalline or amorphous, anhydrous or with constitutional water) searching for the particular one capable of promoting the electrochemi- cal properties. According to the first investigations [1–3], the hydrated amorphous FePO 4 shows a superior electrochemical performance, due to the faster ionic diffusion promoted by the hydration water [1]. Prosini et al. succeeded in measuring the dif- fusion coefficient for amorphous FePO 4 ·1.5H 2 O, the very low value was related to the low electronic conductivity of the mate- rial [3]. The electrode did not show a high specific capacity, but the good rechargeability was related to its amorphous character. 0378-7753/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2007.06.176