High-Entropy Li-Rich Layered Oxide Cathode for Li-Ion Batteries

High-entropy oxides (HEOs) have shown significant promise as cathode materials for Li-ion batteries (LIBs) due to their stable solid-state phase and flexible composition. This research explores the structural and electrochemical characteristics of a new non-equimolar high-entropy cathode material, called high-entropy Li-rich layered oxide (HE-LLO, Li1.15Na0.05Ni0.19Mn0.56Fe0.02Mg0.02Al0.02O1.97F0.03), and compares it to a traditional Li-rich layered oxide (PR-LLO, Li1.2Ni0.2Mn0.6O2). By incorporating various cations (Na+, Al3+, Mg2+, Fe3+) and an anion (F-), HE-LLO achieves greater compositional diversity and structural stability through entropy stabilization. Theoretical calculations indicate that HE-LLO has significantly higher configurational entropy than PR-LLO, supporting its high-entropy status. Electrochemical tests reveal that HE-LLO retains 76.8% of its discharge capacity at 0.5C after 200 cycles, while PR-LLO retains only 36.2%. At elevated temperatures (55°C), HE-LLO maintains 76.1% of its discharge capacity after 100 cycles at 5C, while PR-LLO retained only 12.4%. Additionally, HE-LLO demonstrates superior capacity at higher current densities (5C and 10C) compared to PR-LLO. These improvements are attributed to the enhanced phase stability and higher Li+ ion diffusion coefficients in HE-LLO, supported by ex-situ characterizations using both conventional and synchrotron X-ray techniques, and density functional theory (DFT) calculations. This study underscores the potential of non-equimolar HEOs as an innovative design strategy for high-performance LIB cathode materials.