In situ surface modification via KMnO4 pre-oxidation enables air stability and high temperature resistance in LiNi0.83Co0.11Mn0.06O2 cathodes

Abstract

In this work, the effect of potassium permanganate (KMnO₄) pre-oxidation treatment on the electrochemical properties of LiNi_0.83Co_0.11Mn_0.06O₂ (NCM811) cathode materials was investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) tests revealed that the pre-oxidation treatment promoted the oxidation of Ni²⁺ to Ni³⁺and the formation of a stable Mn-rich surface. Electrochemical testing showed that the electrochemical performance of the NCM811 material pre-oxidized with an appropriate amount of KMnO₄ (811–3) was significantly improved at both ambient (25 ℃) and elevated temperatures (55 ℃) compared to the untreated sample. Additionally, the air stability of 811–3 was enhanced. Specifically, the pre-oxidation treatment increased the oxidation state of nickel, minimized side reactions with CO₂ and moisture in the air, and improved cycling stability, rate performance, and lithium-ion diffusion. It also resulted in a lower self-discharge rate, ensuring better long-term voltage retention. These results indicated that KMnO₄ pre-oxidation is an effective strategy for improving the electrochemical performance of NCM811 and has the potential for application to other Ni-rich cathode materials.