Fluorine‐Doping Strategy To Improve the Surface and Electrochemical Properties of LiNi_0.6Co_0.2Mn_0.2O₂ Cathodes for Use in Lithium‐Ion Batteries

Abstract

This study sought to achieve fluorine doping into the surface structure of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes for use in lithium‐ion batteries by the atomic layer deposition method to improve structural stability and electrochemical performance. Thin‐film electrodes were used to clearly understand the fundamental effects of surface properties. Based on our observations, the oxygen vacancy that basically exists in the surface of the NCM622 thin‐film electrode triggers the additional formation of oxygen derivatives with a spinel‐like phase, leading to poor cycling stability and severe deterioration of the surface structure. Contrary, the fluorinated NCM622 thin‐film electrode exhibits improved electrochemical properties including satisfactory cycling stability, which benefits from the higher binding energy of fluorine that positively influences the stability of the surface oxygen layer by being doped into the unstable oxygen site, and thus the formation of oxygen derivative phases is successfully suppressed during electrochemical reactions.

Influence of Tris(trimethylsilyl)phosphite Additive on the Electrochemical Performance of Lithium-ion Batteries Using Thin-film Ni-rich Cathodes

“…The structural characteristics of the prepared NCM622 thin-film electrodes have been comprehensively reported in our previous studies. 8,23 The NCM622 thin-film electrode has a hexagonal structure, which can be assigned to the 𝑅3 ̅ 𝑚 space group. 24 Figure 1 compares the electrochemical performance of NCM622 thin-film electrodes using a solution of BE and that with the addition of 1 wt% TMSPi.…”

“…According to previous studies, a peak at 531.2 eV (green line) can be referred to as the oxygen derivative phases, triggered by the unstable oxygen bond with transition metal ions on the surface of the layer structure, leading to the formation of an oxygen vacancy and structural degradation. 23,34,35 To clarify the degradation stages of thin-film electrodes, in this study we introduced a defect ratio, which represents the ratio of the derivative phases to the total intensity of oxygen components from the NCM structure, including the oxygen of the NCM lattice and derivative phases. The quantified results in Fig.…”

Thin Film Deposition Techniques in Surface Engineering Strategies for Advanced Lithium-Ion Batteries

“…A great contribution has been acquired by introducing film deposition techniques for surface coating. Besides, the film deposition techniques have the functions of doping, nanostructuring, and formation of active materials [132][133][134][135][136][137][138][139][140]. Therefore, from the perspective of advanced thin film deposition techniques, it is particularly significant for the development of lithium-ion batteries to deeply investigate the related works to emphasize the understanding as well as smart applications.…”