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

In this study, the electrochemical performance of LiNiO ₂ is obviously improved via a method of precursor peroxidation with K ₂S ₂O ₈ 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 LiNiO ₂ has an lowered Li ⁺/Ni ²⁺ cation-mixing. SEM and TEM results show that the surface of N30 LiNiO ₂ 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 LiNiO ₂ 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 LiNiO ₂. In addition, the discharge capacity of N30 LiNiO ₂ at 5 C is ∼ 150 mAh g ⁻¹, which is much higher than that of the original LiNiO ₂ (∼ 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 LiNiO ₂ materials.