High-Entropy Layered Oxide Cathode Enabling High-Rate for Solid-State Sodium-Ion Batteries

Na-ion O3-type layered oxides are prospective cathodes for Na-ion batteries due to high energy density and low-cost. Nevertheless, such cathodes usually suffer from phase transitions, sluggish kinetics and air instability, making it difficult to achieve high performance solid-state sodium-ion batteries. Herein, the high-entropy design and Li doping strategy alleviate lattice stress and enhance ionic conductivity, achieving high-rate performance, air stability and electrochemically thermal stability for Na(0.95)Li(0.06)Ni(0.25)Cu(0.05)Fe(0.15)Mn(0.49)O(2). This cathode delivers a high reversible capacity (141 mAh g(−1) at 0.2C), excellent rate capability (111 mAh g(−1) at 8C, 85 mAh g(−1) even at 20C), and long-term stability (over 85% capacity retention after 1000 cycles), which is attributed to a rapid and reversible O3–P3 phase transition in regions of low voltage and suppresses phase transition. Moreover, the compound remains unchanged over seven days and keeps thermal stability until 279 ℃. Remarkably, the polymer solid-state sodium battery assembled by this cathode provides a capacity of 92 mAh g(−1) at 5C and keeps retention of 96% after 400 cycles. This strategy inspires more rational designs and could be applied to a series of O3 cathodes to improve the performance of solid-state Na-ion batteries. [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40820-023-01232-0.