Synthesis and Electrochemical Performance of 0.3Li₂MnO₃·0.7LiMO₂ (M = Mn, Co, Ni) Cathode Materials for Li-Ion Batteries

Abstract

The Mn0.720Ni0.175Co0.105(OH)2 precursor was co-precipitated by the Couette-Taylor reactor. The 0.3Li2MnO3 x 0.7LiMn0.60Ni0.25Co0.15O2 of the high capacity cathode material for a Li-ion battery was synthesized according to the amount of lithium excess (5-20 mol.%). X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) were used to characterize the 0.3Li2MnO3 x 0.7Li-Mn0.60Ni0.25Co0.15O2. Based on the XRD patterns and FE-SEM images, the 5 and 10 mol.% lithium excess samples were observed for spinel structure. The 15 and 20 mol.% lithium excess samples were not observed for the structure. We can conclude that the spinel structure was made in 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2, due to a lack of lithium. The discharge specific capacity of 5, 10, 15, and 20 mol.% lithium excess were measured at 216, 246, 262, and 261 mA h g(-1), respectively. Cyclic voltammograms show that the Li2MnO3 has a lower lithium influence than a spinel or layered structure. Based on these experiment results, we can conclude that the best Li source amount of the 0.3Li2MnO3 x 0.7LiMn0.60-Ni0.25Co0.15O2 synthesis is a 15 mol.% excess.

Effects of Lithium Content and Surface Area on the Electrochemical Performance of Li1.2Mn0.54Ni0.13Co0.13O2

“…18 Ryu et al used a Couette-Taylor reactor to co-precipitate 0.3Li 2 MnO 3 • 0.7LiMn 0.60 Ni 0.25 Co 0.15 O 2 and found that 15 mol% excess lithium was necessary to form the desired layered compound. 19 Deng et al found that co-precipitated materials are very sensitive to lithium concentration, and lithium deficiency in the precursor solution can lead to the formation of spinel LiNi 0.5 Mn 1.5 O 4 upon lithiation, which was found to improve the rate capability of the materials upon cycling. 8,13 Since many synthesis methods are used to prepare the layered cathodes, different annealing conditions are applied to the as-synthesized powders, and this is sometimes combined with a post-lithiation reaction.…”

“…8,13 Since many synthesis methods are used to prepare the layered cathodes, different annealing conditions are applied to the as-synthesized powders, and this is sometimes combined with a post-lithiation reaction. 6,8,19 Generally, as the annealing time and temperature increase the primary particles undergo coarsening. [20][21][22] However, it has also been observed that increasing the lithium content of the material promotes coarsening and thus, reduces surface area.…”