Journal of Power Sources 160 (2006) 627–632 Electrochemical characteristics of layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 and with different synthesis conditions Ping He a,∗ , Haoran Wang b , Lu Qi a , Tetsuya Osaka c a Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China b Beijing Green Power and Technology Company Ltd., Beijing 100001, PR China c Department of Applied Chemistry, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan Received 13 December 2005; received in revised form 17 January 2006; accepted 18 January 2006 Available online 28 February 2006 Abstract LiNi 1/3 Mn 1/3 Co 1/3 O 2 had been successfully prepared from spherical composite carbonate via a simple uniform-phase precipitation method [P. He, H. Wang, L. Qi, T. Osaka, J. Power Sources, in press] at normal pressure, using nickel, cobalt and manganese sulfate and ammonia bicarbonate as reactants. The preparation of spherical composite carbonate was significantly dependant on synthetic condition, such as the reaction temperature, feed rate, molar ratio of these reactants, etc. The optimized condition resulted in spherical composite carbonate of which the particle size distribution was uniform, as observed by scanning electronic microscopy (SEM). Calcination of the uniform composite carbonate with lithium carbonate at high temperature led to a well-ordered layer structured LiNi 1/3 Mn 1/3 Co 1/3 O 2 as confirmed by X-ray diffraction (XRD), without obvious change in shape. Due to the homogeneity of the composite carbonate, the final product, LiNi 1/3 Mn 1/3 Co 1/3 O 2 , was also significantly uniform, i.e., the average particle size was of about 10 m in diameter and the distribution was relatively narrow. As a result, the corresponding tap density was also high, approximately 2.32 g cm -3 , of which the value is very near to that of commercialized LiCoO 2 . In the voltage range of 2.8–4.2, 2.8–4.35 and 2.8–4.5V, the discharge capacities of LiNi 1/3 Mn 1/3 Co 1/3 O 2 electrode were 159, 168 and 179 mAh g -1 , respectively, with good cyclability. © 2006 Published by Elsevier B.V. Keywords: Spherical; Composite carbonate; Uniform-phase precipitation; Lithium-ion cell; Cathode material 1. Introduction Currently, the most widely used cathode material in lithium- ion secondary battery is LiCoO 2 , because of its simple pro- ducing process, high specific capacity and long circle life [1]. While concerning about the relatively high cost of cobalt, its safety when abused and the interesting higher specific capacity had led to the study of some new cathode materials, such as LiNi x Co 1-x O 2 , LiFePO 4 and LiNi x Co y Mn 1-x-y O 2 . The optimum electrode material should combine lower cost as well as greater safety and performance compared to LiCoO 2 . The sample had lower cost for the use of nickel and man- ganese, which were both abundant in the lithosphere. When it was charged to 4.6V and then discharged to 2.5V, it man- ifested the specific capacity of 200 mAh g -1 , which was higher ∗ Corresponding author. Tel.: +86 10 6275 3288; fax: +86 10 6275 5290. E-mail address: heping@pku.edu.cn (P. He). than LiCoO 2 without sacrificing circle life. Having been charged to 4.4 V and analyzed by thermogravimetry/differential thermal analysis (TG/DTA), it had much less heat flow and higher onset temperature than LiCoO 2 . LiNi 1/3 Mn 1/3 Co 1/3 O 2 was first proposed by Ohzuku and Makimura [2]. They initially prepared it by solid state reaction method and re-prepared by mixed hydroxide method [3]. Chow- dari and co-workers [4] also prepared it at 1000 ◦ C by mixed hydroxide method and reported that the predominant oxidation states of Ni, Co and Mn in the compound were 2 + ,3 + and 4 + , respectively. However, a closer inspection of their results reveals some contradictory information on the electrochemical behav- ior, such as the shape of initial charge curve, reversible capacity and cyclic performance. This strongly implied that the elec- trochemical characteristics of LiNi 1/3 Mn 1/3 Co 1/3 O 2 are prone to be affected by preparation condition. Li et al. studied [5] the influence of preparation method on the structural and elec- trochemical characteristics of LiNi 1/3 Mn 1/3 Co 1/3 O 2 in order to further improve its electrochemical performance, and found that 0378-7753/$ – see front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.jpowsour.2006.01.053