Preparation and Electrochemical characteristics of Li[Ni0.5Mn0.5]O2 using NaOH coprecipitation

Abstract

The commercially Lithium ion batteries make use of layered LiCoO2 cathode, but the high cost, toxicity is motivating low cost, non-toxicity cathode material. In this regard the layered Li[Ni0.5Mn0.5]O2 has been attractive candidate for lithium ion battery and many researchers have reported electrochemical property and synthesis using manganese-nickel hydroxide [1-2]. Metal hydroxide for using NaOH coprecipitation have been applied in the alkaline rechargeable batteries and Li-ion batteries and used in points of low cost [3-4]. In this work, we have been researched manganese-based metal hydroxide precipitation in electrochemical properties, morphology and high-tap density for lithium ion battery. Experimental Manganese-nickel double hydroxide was prepared by feeding an aqueous solution of nickel and manganese sulfate, an aqueous solution of sodium hydroxide and an additive into a reactor under stirring in nitrogen atmosphere. The concentration, feed rate, temperature and pH of the mixture were all controlled. (Ni0.5Mn0.5)(OH)2 was extracted continuously from the reactor, then washed and dried at 110℃ without grinding. Nickel-manganese hydroxide had an average size of 10㎛. Li[Ni0.5Mn0.5]O2 was prepared by using appropriate amounts of LiOH?H2O and manganese-nickel hydroxide. the mixed powder was preheated at 480℃ for 10hr, calcined at 1000℃ for 15hr and cooled slowly(2℃/min). Powder X-ray diffraction (Rigaku, Rint-2000) using CuKα radiation was used to identify the crystalline phase of the as-prepared powders. Charge-discharge cycles were performed in CR2032 button type cells and used electrolyte was a 1:2 mixture of EC and DMC containing 1M LiPF6 by volume Result and discussion Li[Ni0.5Mn0.5]O2 has the α-NaFeO2 structure with space group R_3m, which is characteristic of the layered LiCoO2 and LiNiO2 structures. The lattice constants, a and c of Li[Ni0.5Mn0.5]O2 calculated by rietveld refinement from the X-ray diffraction data is a = 2.8885?, c = 14.2882?, and c/a ratio is 4.947 in Fig 1. The Li[Ni0.5Mn0.5]O2 electrode delivers a discharge capacity of 153 mA h g-1 between 2.8 and 4.3 V at current density of 0.2 mA cm-2 (20 mA g-1) in Fig 2.