Rational engineering of high-entropy oxides for Li-ion battery anodes with finely tuned combustion syntheses

High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stabilities and rate capabilities. However, the conventional syntheses and screening processes are time-consuming and complex and require phase and interfacial segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion syntheses with different fuel-to-oxidizer ratios (φ). A slightly lean fuel mixture (φ-0.95) enabled a suitable temperature and non-reducing atmosphere for optimal HEO syntheses. This provided high crystallinity, perfectly homogeneous elemental distributions, and adequate pore structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios resulted in excessively porous morphologies or elemental segregation. HEO-based anodes with φ-0.95 exhibited outstanding specific capacities (1165 mAh g⁻¹, 80.9% retention at 0.1 A g⁻¹_, and 791 mAh g⁻¹ even at 3 A g⁻¹), excellent rate capabilities, and stable cycling lifetimes (1252 mAh g⁻¹, 80.9% retention after 100 cycles at 0.2 A g⁻¹). This design strategy will provide fascinating HEO electrodes that cannot be prepared with conventional fabrication methods.