Journal of Power Sources 159 (2006) 254–257 Short communication Synthesis of NiO nanotubes for use as negative electrodes in lithium ion batteries S.A. Needham ∗ , G.X. Wang, H.K. Liu Energy Storage Materials Group, Institute for Superconducting & Electronic Materials, University of Wollongong, Northfields Ave, Gwynneville NSW 2522, Australia Available online 30 May 2006 Abstract Nickel oxide (NiO) nanotubes have been produced for the first time via a template processing method. The synthesis involved a two step chemical reaction in which nickel hydroxide (Ni(OH) 2 ) nanotubes were firstly formed within the walls of an anodic aluminium oxide (AAO) template. The template was then dissolved away using concentrated NaOH, and the freed nanotubes were converted to NiO by heat treatment in air at 350 ◦ C. Individual nanotubes measured 60 m in length with a 200 nm outer diameter and a wall thickness of 20–30 nm. The NiO nanotube powder was used in Li-ion cells for assessment of the lithium storage ability. Preliminary testing indicates that the cells demonstrate controlled and sustainable lithium diffusion after the formation of an SEI. Reversible capacities in the 300 mAh g -1 range were typical. © 2006 Elsevier B.V. All rights reserved. Keywords: Li-ion batteries; Lithium storage; Nickel oxide; Template method; Nanotubes 1. Introduction Li-ion batteries are now commonly utilized in popular elec- tronic equipment, such as mobile telephones, laptop computers, and digital cameras. However, the next generation of portable appliances are being developed at an astounding rate. These new products will require more powerful and versatile energy storage systems. If Li-ion batteries are to be considered the bat- tery of choice in the future, then significant improvements in the stored energy density and cyclability must occur. In addi- tion, any advances in the performance of the battery must be achieved without sacrificing important safety aspects. For Li- ion batteries, the key to satisfying these objectives rests with the manufacture of electrode materials that have nanoscale dimen- sions (nanomaterials) [1]. It is well known that physical and chemical phenomena can be vastly different in a nanomaterial compared to those observed in its bulk state. This point is clearly illustrated in the transition metal oxide (MO) system (M = Fe, Co, Cu, Ni) by consider- ing the applicability of these materials to Li-ion batteries. In this system, the reaction of the MO with lithium results in the formation of the reduced metal and lithia (Li 2 O). It had long ∗ Corresponding author. Tel.: +61 2 422 13733; fax: +61 2 422 15731. E-mail address: scott needham@uow.edu.au (S.A. Needham). been reported that bulk Li 2 O was electrochemically inactive and therefore unable to be decomposed. However, by manufactur- ing nanostructured MO precursors, the resultant Li 2 O is also nanostructured and may be decomposed [2,3]. This finding has allowed the reaction of nanostructured MOs with lithium to be made completely reversible and meant that these materials have received significant attention as possible candidates for use in Li-ion batteries. Early reports have shown that irregularly shaped MO nanoparticles can exhibit reversible capacities up to 700 mAh g -1 [2]. This capacity is almost three times larger than that of the graphite based negative electrodes that are used in commercial rechargeable batteries. Of the wide range of nanostructures that are now feasible, the nanotube represents an ideal one-dimensional topology that can allow controlled Li + diffusion over many charge–discharge cycles [4]. This effect may be attributed to the high surface area and low diffusion distance for solid state Li-ion transport. Indeed, there have been recent reports on the synthesis of nanotubes made from V 2 O 5 [5,6], TiO 2 [7], and Co 3 O 4 [8] materials that demonstrate excellent electrochemical properties. However, progress on new transition MOs has been sparse, presumably due to the difficult nature of material synthesis. Nickel oxide is an important member of this group that shows potential as a chemical sensor and, in particular, as a negative electrode in Li-ion batteries. 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.04.025