Synthesis of pure phase disordered LiMn 1.45 Cr 0.1 Ni 0.45 O 4 by a post-annealing method D. Liu a , J. Hamel-Paquet a , J. Trottier a , F. Barray a , V. Gariépy a , P. Hovington a , A. Guerfi a , A. Mauger b , C.M. Julien c , J.B. Goodenough d , K. Zaghib a, * a Energy Storage and Conversion, Research Institute of Hydro-Québec, Varennes, Québec, Canada J3X 1S1 b Université Pierre et Marie Curie e Paris 6, Institut de Minéralogie et Physique de la Matière Condensée (IMPMC), 4 place Jussieu, 75005 Paris, France c Université Pierre et Marie Curie e Paris 6, Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques (PECSA), UMR 7195, 4 place Jussieu, 75005 Paris, France d The University of Texas at Austin, Austin, TX 78712, USA highlights < High purity LiMn 1.45 Cr 0.1 Ni 0.45 O 4 has been obtained. < The B-site of the spinel is partially ordered at the scale of the nearest neighbors, fully disordered at the scale of the nanometer. < The electrochemical properties are improved with respect to a commercial sample. article info Article history: Received 16 May 2012 Received in revised form 14 June 2012 Accepted 16 June 2012 Available online 23 June 2012 Keywords: Li-ion 5V system Cathode LiMn 1.45 Cr 0.1 Ni 0.45 O 4 Post-annealing abstract A post-annealing strategy at 600  C was used to modify the oxygen deficiency during synthesis of a spinel LiMn 1.45 Cr 0.1 Ni 0.45 O 4 cathode for lithium-ion batteries. Structural analyses revealed that post- annealing is an effective way to eliminate the impurity phase without changing the Fd 3m space group. The substitution of a small amount of Cr leads to better rate performance along with cyclability at room temperature, compared to the commercial LiMn 1.5 Ni 0.5 O 4 . LiMn 1.45 Cr 0.1 Ni 0.45 O 4 delivered a reversible capacity of w115, 104, 95 and 40 mAh g 1 at 0.2C, 1C, 2C and 5C, respectively. While commercial LiMn 1.5 Ni 0.5 O 4 offered a lower reversible capacity of w110, 98, 85 and 20 mAh g 1 at the same C rates. After 125 cycles, about 99% of reversible capacity was retained for the LiMn 1.45 Cr 0.1 Ni 0.45 O 4 , while about 6% of capacity loss was obtained after 125 cycles for the commercial LiMn 1.5 Ni 0.5 O 4 . Elec- trochemical impedance spectroscopy measurements revealed that the LiMn 1.45 Cr 0.1 Ni 0.45 O 4 had a smaller surface resistance, which may be due to the segregation of Ni from the surface to the bulk. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Developing cathode materials with high energy densities is one of the key challenges for adopting the lithium-ion battery tech- nology for hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV) applications. A high energy density can be obtained either by high voltage or high capacity [1,2]. With a high operating voltage around 4.7 V and a practical capacity (about 130 mAh g 1 ) comparable to that of LiCoO 2 (w140 mAh g 1 ) and LiFePO 4 (w160 mAh g 1 ), spinel LiMn 1.5 Ni 0.5 O 4 provides a higher specific energy (w610 Wh kg 1 ) than many commercialized compounds. Previous studies in the literature have reported that there are two types of LiMn 1.5 Ni 0.5 O 4 (denoted LMN) depending on the ordering of Ni/Mn in the octahedral sites, a disordered LMN and an ordered LMN [3e6]. In the disordered spinel, where transition- metal ions are randomly distributed at octahedral 16d sites, the Fd 3m space group is observed. The Li at a tetrahedral 8a site moves via a vacant octahedral 16c site in an 8a-16c diffusion path. In contrast, the ordered LMN has a P4 3 32 space group with Li atoms located at 8c sites; the octahedral vacant 16c sites are split into ordered 4a and 12d sites with a ratio of 1:3 to form diffusion paths 8c-4a and 8c-12d (Fig. 1). Ordering of the Ni(II) and Mn(IV) retards the lithium diffusivity [7] and therefore lowers the rate capability [3,8,9]. However, the synthesis of disordered LMN is often accompanied by oxygen loss at high temperature (>715  C), which results in nonstoichiometric LiMn 1.5 Ni 0.5 O 4d [3]. Oxygen deficiency in LMN * Corresponding author. Tel.: þ1 450 652 8019; fax: þ1 450 652 8424. E-mail address: zaghib.karim@ireq.ca (K. Zaghib). Contents lists available at SciVerse ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour 0378-7753/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jpowsour.2012.06.063 Journal of Power Sources 217 (2012) 400e406