Mitigating the rock-salt phase transformation in disordered LNMO through synergetic solid-state AlF3/LiF modifications

Abstract

High-voltage disordered spinel LiNi0.5Mn1.5O4 is a promising cathode material for high power density in lithium-ion batteries. However, it suffers from poor cycle life associated with the rock-salt phase transformation. This study presents a straightforward synthesis approach to enhance the electrochemical performance of LiNi0.5Mn1.5O4 through a synergistic solid-state modification with LiF and AlF3. This dual modification promotes rapid Li¿ diffusion, enables near-complete delithiation/lithiation, approaching the theoretical capacity of disordered LiNi0.5Mn1.5O4, and, more importantly, effectively mitigates the formation of the rock-salt phase, thereby enhancing structural stability, as confirmed by operando X-ray absorption spectroscopy (XAS) and synchrotron X-ray diffraction (SXRD). As a result, the optimized LiNi0.5Mn1.5O4 (10 mg AlF3 + 30 mg LiF) delivers high reversible capacities of 142.1, 139.1, 129.2, 121.6, 110.3, 93.5, and 76.1 mAh·g-1 at 0.2C, 0.5C, 1.0C, 2.0C, 3.0C, 4.0C, and 5.0C, respectively. Full cells using graphite as the anode and a high-loading cathode exhibit excellent cycling performance. They retain 80% of their capacity after 200 cycles at 0.5C within a voltage window of 3.5–4.9 V with cathode loading of 11 mg·cm-2. The findings of this study will significantly advance high-power LiNi0.5Mn1.5O4 materials, offering improved battery life and thereby enhancing their potential for practical applications.

This work was supported by the European Commission-financed project IntelLigent (HORIZON-CL5-2021-D2-01-02) with project ID number 101069765. In collaboration with ALBA staff, the operando SXRD and XAS experiments were performed at BL-16-NOTOS beamline at ALBA Synchrotron Light Source (experiment number: 2023097765). This research was supported by the Scientific Service Units (SSU) of the Institute of Science and Technology Austria (ISTA) through resources provided by the Electron Microscopy Facility (EMF) and the Nanofabrication Facility (NFF), and M.I. and S.H. acknowledge financial support from ISTA and the Werner Siemens Foundation. Jordi Jacas Biendicho acknowledges the fellowship RYC2021-034994-I, funded by MICIU/AEI/10.13039/501100011033 and the European Union «NextGenerationEU»/PRTR». Jordi Llorca is a Serra Húnter Fellow and is grateful to projects MICIN/AEI/FEDER PID2021-124572OB-C31 and Maria de Maeztu Units of Excellence Programme CEX2023-001300-M, and GC 2021 SGR 01061.

Postprint (published version)