Journal of Power Sources 196 (2011) 8625–8631 Contents lists available at ScienceDirect Journal of Power Sources jo ur nal homep age: www.elsevier.com/locate/jpowsour Li(Ni 0.40 Mn 0.40 Co 0.15 Al 0.05 )O 2 : A promising positive electrode material for high-power and safe lithium-ion batteries J. Bains a,b , L. Croguennec a,b , J. Bréger c,∗ , F. Castaing c , S. Levasseur d , C. Delmas a,b , Ph. Biensan c a CNRS, Université de Bordeaux, ICMCB, 87 av. Schweitzer, Pessac, F-33608, France b IPB, ENSCBP, ICMCB, Pessac, F-33608, France c SAFT, Direction de la Recherche, 111-113 Bld Alfred Daney, Bordeaux, F-33074, France d UMICORE Research & Development, Kasteelstraat 7, B-2250 Olen, Belgium a r t i c l e i n f o Article history: Received 17 January 2011 Received in revised form 6 May 2011 Accepted 3 June 2011 Available online 12 June 2011 Keywords: Lithium-ion battery Positive electrode material Layered oxide Aluminium substitution X-ray diffraction Power electrochemical performance Thermal stability a b s t r a c t Li 1.11 (Ni 0.40 Mn 0.39 Co 0.16 Al 0.05 ) 0.89 O 2 was synthesized through coprecipitation of a mixed hydroxide fol- lowed by calcination with LiOH·H 2 O during 10 h at 500 ◦ C and 950 ◦ C. Electrochemical tests and their comparison with those obtained for an industrial Li(Ni 1-y-z Co y Al z )O 2 material reveal that Li 1.11 (Ni 0.40 Mn 0.39 Co 0.16 Al 0.05 ) 0.89 O 2 shows good charge–discharge performance, even at high rate accord- ing to a protocol well established by car-makers for testing power abilities of batteries for electric and hybrid electric vehicles. In addition, this material shows a significant improvement in thermal stability in the highly deintercalated state (charged state of the battery) over the industrial material. Equivalent (or higher) energy and power densities with a significantly greater thermal stability make of Li 1.11 (Ni 0.40 Mn 0.39 Co 0.16 Al 0.05 ) 0.89 O 2 an interesting candidate as positive electrode material for large lithium-ion batteries. © 2011 Elsevier B.V. All rights reserved. 1. Introduction During the past decade, rechargeable lithium batteries have been much investigated and widely used because they potentially have a large range of applications [1]; they are not only required to enable the fairly charge/discharge rates applications like mobile phone and portable computer but also to meet an increasing need for new applications such as electric vehicles (EV) or hybrid elec- tric vehicles (HEV) [2]. Unlike most of the applications, where the energy density or the capacity of the batteries is the most relevant concern, HEV applications require batteries with high power. The cell capacity is related to the amount of active lithium ions that are able to shuttle between the positive and negative electrodes under the operating conditions, while the power of a cell is directly related to the cell impedance or internal resistance [3]. More importantly, for battery applications the capacity fade is not necessarily associ- ated with a power fade, and vice versa. Therefore, it is essential to develop lithium-ion batteries with small and stable cell impedance [4]. LiCoO 2 shows high energy density and cycling stability that make it an excellent positive electrode candidate for batteries used ∗ Corresponding author. Tel.: +33 5 5710 6899, fax: +33 5 5710 6414. E-mail address: Julien.Breger@saftbatteries.com (J. Bréger). in portable applications, but it has also some disadvantages such as poor thermal stability, inferior overcharge characteristics and toxicity. Since the newly developed EV and HEV require high volu- metric energy density and thermal stability over those of LiCoO 2 it accelerates intensive researches to find an alternative positive elec- trode material for high energy applications. For instance, since the pioneering work of Goodenough et al. [5], olivine LiFePO 4 positive electrode materials were shown to exhibit excellent overcharge characteristics and good chemical and thermal stability [6], with low toxicity and low cost, which make them particularly attrac- tive for high-power applications. The main drawback of LiFePO 4 remains its low discharge potential (3.45 V vs. Li + /Li) that limits the energy density delivered by this material (15% less than for LiCoO 2 ). In fact, its low ionic and electronic conductivities at first very detri- mental to good transport properties were overcome by forming carbon coated nanomaterials [7]. Layered lithium nickel manganese oxides are also promising and inexpensive alternative positive electrode materials to the com- mercial LiCoO 2 electrode materials used in most of the lithium-ion batteries. Among these, LiNi 0.5 Mn 0.5 O 2 shows quite low Li diffusiv- ity and thus charge/discharge rates because of the high ratio of Ni cations present in the Li layers [8,9], making it not satisfying the high power requirements in HEV applications. Recently, an other layered transition metal oxide, Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 , was intro- duced by Ohzuku and Makimura [10] as a good candidate as positive 0378-7753/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2011.06.016