Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods

Abstract

The lithiated nickel-cobalt oxide LiNi 0.5 Co 0.5 O 2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi 0.5 Co 0.5 O 2 products calcined at 400-600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi 0.5 Co 0.5 O 2 compounds. Thermal (TG-DTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO 4 in propylene carbonate, PC). The LiNi 0.5 Co 0.5 O 2 positive electrodes fired at 600°C exhibited good cycling behavior.

Surface properties of LiCoO2, LiNiO2 and LiNi1−xCoxO2

“…The XRD data are characteristic of the materials, although the LiNi 0.5 Co 0.5 O 2 trace appears broader than that of the other samples even after extensive efforts were made to optimize synthesis conditions for this mixed transition metal oxide. Similar quality XRD are found for LiNi 0.5 Co 0.5 O 2 powders elsewhere in the literature [13], [40] and [41], indicating that it is diffi cult to form a truly homogenous solid solution in which nickel and cobalt are randomly distributed within the (1 1 1) transition metal planes. Not surprisingly, unit cell dimensions increase with increasing nickel content for the hexagonal samples, which is evident through a decrease in 2θ for diffraction from a particular lattice plane.…”

“…LiNi 0.5 Co 0.5 O 2 samples were also synthesized by sol-gel methods [39] and [40]. Li(CH 3 CO 2 ) 2 ·4H 2 O, Ni(CH 3 CO 2 ) 2 ·4H 2 O and Co(CH 3 CO 2 ) 2 ·4H 2 O (Aldrich, 98%) in appropriate stoichiometry were co-dissolved in distilled water.…”

Nanotechnology for Energy Storage

“…The wet-chemical techniques could be classified in four groups according the salts and complexing agent used (Table 12.1). They are namely sol-gel [9,10], co-precipitation [11,12], combustion [13], pyrolysis [14], polyol [15], Pechini process [16,17], etc. ; they were employed for the preparation of nanostructured metal oxides devoted to electrodes for Li-ion batteries.…”

Critical review on lithium-ion batteries: are they safe? Sustainable?

“…To reduce this cation mixing, Co is introduced in the matrix efficiently, as it stabilizes the layered structure in LiNi 1-y Co y O 2 [8]. As a consequence, the electrochemical properties are improved.…”