Theoretical Prediction of Surface Stability and Morphology of LiNiO₂ Cathode for Li Ion Batteries

Abstract

Ni-rich layered oxides are considered to be a promising cathode material with high capacity, and their surface structure should be extensively explored to understand the complex associated phenomena. We investigated the surface stability and morphology of LiNiO as a representative of these materials by using density functional theory calculations. The results reveal that the Li-exposed surfaces have lower energies than the oxygen surfaces, irrespective of the facets, and the Ni-exposed ones are the least stable. The equilibrium morphology can vary from truncated trigonal bipyramid to truncated egg shape, according to the chemical potential, whose range is confined by the phase diagram. Moreover, the electrochemical window of stable facets is found to strongly depend on the surface elements rather than the facet directions. Contrary to the stable Li surfaces, oxygen exposure on the surface considerably lowers the Fermi level to the level of electrolyte, thereby accelerating oxidative decomposition of the electrolyte on the cathode surface.

There and Back Again—The Journey of LiNiO2 as a Cathode Active Material

“…In LNO, the Ni content is higher and so is the reactivity. Indeed, recent computational results revealed that polar facets with exposed oxygen lower the Fermi energy of the material, thereby facilitating electron transfer from the electrolyte . The same authors also showed that, in general, Ni‐exposed surfaces are the least stable ones, while Li‐exposed ones are the most stable.…”

A Comprehensive Analysis of the Interphasial and Structural Evolution over Long‐Term Cycling of Ultrahigh‐Nickel Cathodes in Lithium‐Ion Batteries

“…[7,80] Specifically, a stoichiometric amount of aluminum isopropoxide (≥99.99%, Sigma-Aldrich) was dissolved in isopropanol solvent (99.7%, Sigma-Aldrich) at 60 °C and then mixed with the Ni 0.94 Co 0.06 (OH) 2 precursor with magnetic stirring until the solution was dried to yield Al(OH) 3 , and poly(vinylidene) fluoride (PVDF) (HSV900, ≥99.5%, MTI Corp.) with a mass ratio of 8: 1: 1 were mixed in N-methyl-2-pyrolidone (NMP) (99%, Sigma-Aldrich) under vigorous stirring to form a black slurry. [7,80] Specifically, a stoichiometric amount of aluminum isopropoxide (≥99.99%, Sigma-Aldrich) was dissolved in isopropanol solvent (99.7%, Sigma-Aldrich) at 60 °C and then mixed with the Ni 0.94 Co 0.06 (OH) 2 precursor with magnetic stirring until the solution was dried to yield Al(OH) 3 , and poly(vinylidene) fluoride (PVDF) (HSV900, ≥99.5%, MTI Corp.) with a mass ratio of 8: 1: 1 were mixed in N-methyl-2-pyrolidone (NMP) (99%, Sigma-Aldrich) under vigorous stirring to form a black slurry.…”

Hin und zurück – die Entwicklung von LiNiO2 als Kathodenaktivmaterial

“…In LNO ist der Ni‐Gehalt höher und damit auch die Reaktivität gegenüber dem Elektrolyten. Tatsächlich ergaben jüngste Rechnungen, dass polare Facetten mit freiliegendem Sauerstoff die Fermi‐Energie des Materials senken und den Elektronentransfer aus dem Elektrolyten erleichtern . Die gleichen Autoren zeigten auch, dass im Allgemeinen Ni‐exponierte Oberflächen die am wenigsten stabilen sind, Li‐exponierte Oberflächen hingegen die stabilsten.…”