Depth-Resolving the Charge Compensation Mechanism from LiNiO₂ to NiO₂

Abstract

The performances of lithium-ion batteries depend on the capability of the electrode materials to exchange lithium ions and electrons faster and reversibly. LiNiO 2 is a promising electrode candidate for achieving high voltage and capacity. However, its industrialization is hindered by surface and bulk instabilities. These instabilities are due to redox processes involving charge transfer between the cations and anions. Therefore, a fundamental understanding based on further experimental evidence is required to resolve the charge transfer between the cation and anion from the surface to the bulk in LiNiO 2 . Herein, we resolve the roles of nickel and oxygen in the charge compensation process in Li x NiO 2 electrodes from the extreme surface down to 30 nm by energy dependent core-level HAXPES supported by an ab initio simulation. We emphasize the central role of oxygen in the bulk charge compensation mechanism from LiNiO 2 to NiO 2 due to the negative charge transfer and bond/charge disproportionation characters of LiNiO 2 .

Effects of sulfate modification of stoichiometric and lithium-rich LiNiO2 cathode materials

“…All of these binding energy values are representative of the nickel environments in LiNiO 2 . 43,44 HAXPES and XPS spectra were collected to investigate the presence of S dopant in the bulk and on the surface of S-LNRO, respectively. XPS and HAXPES spectra of S 2p of S-LRNO are shown in Fig.…”