Electrode reaction of niobium chalcogenides as positive electrodes for secondary lithium batteries

Abstract

The structural changes and electrochemical behavior of Nb dichalogenide electrodes for lithium batteries were investigated in various electrolytes such as 1 M LiClO 4 + propylene carbonate, 1 M LiClO 4 + dimethyl sulfoxide, etc. For 3R-NbS 2, a bare Li + ion is intercalated into the Van der Waals layers by the discharge, and the c-lattice parameter and open circuit potential vary monotonically with discharge, suggesting the formation of a single ternary phase, Li x NbS 2( x=0-1). On the other hand, for 2H-NbS 2, these vary in a stepwise manner with discharge, showing the formation of different ternary phases, and in the discharge product an undischarged part was observed in the inner layer of the sulfide particle. The diffusion coefficient of the Li + ion in 3R-NbS 2 was higher than that in 2H-NbS 2 by one order of magnitude. On the discharge of 2H-NbSe 2 in 1 M LiClO 4 + DMSO, a solvated Li + ion was taken up into the interlayer space accompanying a large expansion in the interlayer spacing, resulting in the formation of a ternary phase, Li x (DMSO) y NbSe 2