Changes in Chemical Bondings by Li Deintercalation in LiMO₂ (M=Cr, V, Co and Ni)

Abstract

First principles molecular orbital calculations for LiMO2 and MO2 have been carried out using the discrete variational Xα cluster method. Li in LiMO2 is nearly completely ionized. Strong covalent interaction between M and O is noted. The removal of Li significantly increases the interaction between M and O. This results in the “oxidation” associated with the de-intercalation not of M but of O. The formal redox notation for the de-intercalation, i.e., M(IV)/M(III), is thus far from reality. The difference in the de-intercalation capability among four LiMO2 compounds is ascribed to the difference in the magnitude of electrostatic repulsion between the oxygen layers in MO2.

Changes in the crystal and electronic structure of LiCoO2 and LiNiO2 upon Li intercalation and de-intercalation

“…The linear increase of the Co/Ni-O bond with increasing Li-content is understandable because antibonding states are filled, and this finding is in agreement with the results from Cluster calculations by van Elp et al 7 and by Koyama et al 25 Experimental evidence supporting these predictions was found by several authors using techniques like XRD, 15 XPS 17,43 and XAFS. 24…”

“…This is in agreement with an XPS study 17 and a theoretical work 18 on Li x CoO 2 , and it is also in agreement with a theoretical work on Li x NiO 2 . 25 One interesting question is the ordering of Li in Li-deprived Li x CoO 2 and Li x NiO 2 . This has been studied intensively in previous theoretical studies.…”

Non-isothermal reaction kinetics of lithium cobalt oxide

“…(10). Based on the authors' previous work [34], the following equation was obtained; The conversion data displayed in Fig.…”

“…The preparation and properties of cathode materials have been intensively studied to improve the electrochemical properties of lithium-ion batteries. Among various cathode materials, lithium cobalt oxide (LiCoO 2 ) is the most commonly used material in lithium-ion batteries because of its high capacity, high working voltage and long cycle life [9,10]. LiCoO 2 has a layered ␣-NaFeO 2 structure that belongs to the R3m space group [11].…”

First principles investigation of electronic structure change and energy transfer by redox in inverse spinel cathodes LiNiVO4 and LiCoVO4

“…Lithium ion batteries have been intensively studied for more than thirty years and the essential mechanisms of charge and energy transfer during lithium ion intercalation are still elusive. [1][2][3][4][5][6][7][8][9] It is expected that each intercalated Li donates one electron completely to the host, which is manifested by the contour plots of charge density, 3 but in conflict with the Mulliken population analysis. 5 From the octet rule, 10,11 the added electron is thought to reduce the transition metal ions in the host.…”