Enhanced electrochemical performance of LiNiO₂ cathode material by precursor preoxidation for lithium-ion batteries

In this study, the electrochemical performance of LiNiO₂ is obviously improved via a method of precursor peroxidation with K₂S₂O₈ in an alkaline medium. XRD, XPS and TEM show that NiOOH was formed on the preoxidized precursor surface. The optimal oxidation time of the precursor is 30 min (N30 precursor), XRD results show that the N30 LiNiO₂ has an lowered Li⁺/Ni²⁺ cation-mixing. SEM and TEM results show that the surface of N30 LiNiO₂ particles is denser and ordered, and the ordered lattice fringes formed two-dimensional pathways that facilitate the diffusion of Li⁺. Charge-discharge test results show that the initial discharge capacity of the original LiNiO₂ is only 177.4 mAh g⁻¹ at 1 C and the capacity retention rate of 100 cycles is 63.9 %. However, the above two data reach to 190.9 mAh g⁻¹ and 88.6 % for N30 LiNiO₂. In addition, the discharge capacity of N30 LiNiO₂ at 5 C is ∼ 150 mAh g⁻¹, which is much higher than that of the original LiNiO₂ (∼ 80 mAh g⁻¹). CV and EIS results indicate that the cycling stability is improved and the charge transfer resistance is reduced. This study provides a better prospect for the commercial application of LiNiO₂ materials.