Structure, Electronic Structure and Defect Formation Energies of Li_xCo_1-yNi_yO₂ as a Function of x (0<x<1) and y (y = 0, 0.5, 1)

Abstract

LixCoO2 and LixNiO2 (0.5&lt;x&lt;1) are prototype cathode materials in lithium ion batteries.Both systems show degradation and fatigue during electrochemical cycling. We have performed band structure calculations based on density-functional theory for a series of compounds Lix(Co,Ni)O2 (0&lt;x&lt;1). The distribution of the transition metals (TM) cobalt and nickel on TM sites as well as the electronic structure of these compounds is investigated with focus on the change of oxidation states of cobalt, nickel and oxygen during lithium de-intercalation. We also study the total energy as a function of the lithium content x, including the vibrational energy E v and the formation energy of lithium vacancies E(VLi). It is found that E v is small compared to E(VLi) and that E(VLi) is increasing with increasing x for all systems.

Lithium and sodium battery cathode materials: computational insights into voltage, diffusion and nanostructural properties

“…85,86 It has also been reported that as-prepared Li(Ni 0.5 Mn 0.5 )O 2 contains 8 to 12% site exchange between Li and Ni, 87 and DFT has been used to explore the effect of this on lithium mobility. 88,89 Fig. 6 shows the calculated activation energy as a function of the distance between the oxygen layers on each side of the Li plane, clearly indicating that more space between the oxygen layers substantially reduces the activation energy.…”

LiMO2 (M = Ni, Co) thin film cathode materials: a correlation between the valence state of transition metals and the electrochemical properties

“…The electronic congurations of LNO and LNCO were the subject of long discussion. [44][45][46][47][48][49][50][51] The main reason for the uncertainty regarding the electronic structure of the LNO-based cathode materials is difficulties in the preparation of the stoichiometric oxides. Recently, based on the SXPS, XPS, HAXPES and NEXAS, it has been shown that the electronic congurations of the Ni and Co ions in the stoichiometric LNCO thin lm material are described as Ni 3+ (t 2g 6 e g 1 , LS) and the Co 3+ (t 2g 6 e g 0 , LS) states.…”

Pushing the boundaries of lithium battery research with atomistic modelling on different scales

“…Experimental studies of mixed-TM layered oxides, such as Li(Ni 0.5 Mn 0.5 )O 2 , have reported site exchange between Li and Ni (∼8%-12%) [687]. DFT has been used to aid in understanding the effects of site-exchange on Li-ion mobility [688,689]. (De)intercalation of lithium in the material changes the distances between the layers.…”

“…As Li is removed from the structure, there is a reduced 'barrier' between the oxygen layers which start to repel one another. By calculating the activation energy as a function of the distance between the O layers on either side of the Li layers, a trend between increased O layer separation and lower activation energy is seen [688,689].…”