Rationally engineered high-entropy oxides using finely tunable combustion synthesis for Li-ion battery anodes

Abstract High-entropy oxides (HEOs) are promising conversion-type anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stability and rate capability. However, their conventional synthesis and screening comprise time-consuming and complex processes involving phase and interface segregation of individual elements. Herein, we report a rational screening strategy for LIB anodes using precisely tunable HEOs fabricated by one-step combustion synthesis with different fuel-to-oxidizer ratios (φ). The slight fuel-lean condition (φ-0.95) facilitates a suitable temperature and anti-reductive atmosphere for the optimal HEO synthesis. This enables high crystallinity, perfectly homogeneous elemental distribution, and adequate porous structures without selective precipitation, whereas lower or higher fuel-to-oxidizer ratios result in forming an excessively porous morphology or the element segregation. HEO-based anodes with φ-0.95 exhibit outstanding specific capacity (1165 mAh∙g -1 , 80.9% retention at 0.1 A∙g -1 , and 791 mAh∙g -1 even at 3 A∙g -1 ), an excellent rate capability, and stable cycling life (1252 mAh∙g -1 , 80.9% retention after 100 cycles at 0.2 A∙g -1 ). This design strategy will inspire fascinating HEO electrodes that cannot be achieved through conventional fabrication methods.