10.26165/JUELICH-DATA/C6G1FF Domgans, Anna0009-0004-9879-2700(IET-1 Forschungszentrum Jülich GmbH)Tranc, Ngoc Thanh Thuy(Hierarchical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung University)Speer, Sebastian0000-00024323-5745(IET-1 Forschungszentrum Jülich GmbH)Kayani, Asghar N(Department of Physics, Dir. Particle accelerator lab, Western Michigan University)Zantis, Frederik0009-0003-6020-9009(IET-1 Forschungszentrum Jülich GmbH)Braun, Tobias0009-0005-5538-646X(IET-1 Forschungszentrum Jülich GmbH)Schaps, Kristian(IET-1 Forschungszentrum Jülich GmbH)Tsai, Chih-Long0000-0001-8103-3514(IET-1 Forschungszentrum Jülich GmbH)Tempel, Hermann0000-0002-9794-6403(IET-1 Forschungszentrum Jülich GmbH)Lin, Shih-kang(Hierarchical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung University;Department of Materials Science and Engineering, National Cheng Kung University;Program on Smart and Sustainable Manufacturing, Academy of Innovative Semiconductor and Sustainable Manufacturing, National Cheng Kung University;Core Facility Center, National Cheng Kung University)Windmüller, Anna0000-0003-2829-3362(IET-1 Forschungszentrum Jülich GmbH)Eichel, Rüdiger-A.0000-0002-0013-6325(IET-1 Forschungszentrum Jülich GmbH, IPC RWTH Aachen University) Jülich DATA 2025 In this study, the layered oxide P2-Na0.66Fe1/3Mn2/3O2 , which is used as a cathode material for sodium ion batteries, was investigated. Layered oxides exhibit phase transitions during the charging/discharging process, which lead to a significant decrease in capacity. One approach to stabilise the structure is the anionic substitution of oxygen. In this study, P2-Na0.66Fe1/3Mn2/3O2 was substituted with various halides F,Cl,Br. The qualitative phase analysis of the PXRD measurements and Raman measurements confirm the successful substitution of 0.02 F in P2-Na0.66Fe1/3Mn2/3O2. This was also confirmed by electrochemical measurements, which showed an improvement in capacity retention of 15 % after 75 cycles for the F-substituted sample compared to the unsubstituted material. Neither for the halogen Cl nor Br could a successful incorporation into the lattice be confirmed, which is due to the larger radii of Cl/Br compared to O. This dataset contains powder X-ray diffraction (PXRD) and Raman measurements, Rutherford Backscattering Spectrometry (RBS), density functional theory (DFT) calculations and electrochemical measurements to investigate halide substitution in P2-Na0.66Fe1/3Mn2/3O2. The dataset is organized into the following folders: PXRD: X-ray diffraction (XRD) experiments were performed using an Empyrean diffractometer (Pananalytical, Almelo, Netherlands). The corresponding diffractograms are stored in the folder PXRD QPA: Qualitative phase analysis (QPA) on the PXRD diffractogramms were conducted using the software package Diffrac.Topas version 7 (Bruker). Data are stored in the folder QPA Raman measurements: Raman spectra were recorded using a WITec Alpha 300R Raman microscope (Ulm, Germany). Data are stored in the folder Raman spectroscopy. RBS: Measurements were conducted using a 1461 keV proton beam. Data are stored in the folder RBS. DFT calculations: Calculations were performed using the Vienna Ab initio Simulation Package (VASP). Data are stored in the folder DFT. Electrochemical experiments: Cyclovoltammetry and galvanostatic charge/discharge experiments were conducted. Data are stored in the folder Electrochemistry. In situ XRD: X-ray diffraction (XRD) experiments were performed using an Empyrean diffractometer (Pananalytical, Almelo, Netherlands). The corresponding diffractograms are stored in the folder in situ XRD For each dataset, detailed experimental procedures and relevant information are provided in the respective folder's ReadMe file. Domgans, Anna(IET-1 Forschungszentrum Jülich GmbH)Windmüller, Anna(IET-1 Forschungszentrum Jülich GmbH)