Decelerating and Accelerating Sulfur Reduction Reaction via P-O_V-In₂O₃ Enables High-Performance Li-S Batteries

The sluggish sulfur reduction reaction (SRR) kinetics of lithium-sulfur (Li-S) batteries seriously limits the development of Li-S batteries. The initial reduction of solid (S₈) to liquid (soluble Li₂S_n (4≤n≤8)) is relatively easy due to the low activation energy, whereas the subsequent conversion of liquid (soluble Li₂S_n) to solid (insoluble Li₂S₂/Li₂S) has much higher activation energy, which leads to the accumulation of Li₂S_n and exacerbates the shuttle effect of Li₂S_n. Therefore, establishing one selective catalyst that decelerates the previous solid-liquid reaction and accelerates the subsequent liquid-solid reaction is essential for rational tailoring of the SRR for improved performance of Li-S batteries, but it represents a daunting challenge. Here, considering that the indium oxide catalyst possesses selective catalytic properties and drawing inspiration from the theoretical calculations, In₂O₃ nanospheres containing phosphorus doping and oxygen vacancies (P-O_V-In₂O₃ NSs) are designed and synthesized as a selective catalyst for Li-S batteries. Contributed by the unique selective catalytic capability, the batteries using P-O_V-In₂O₃ NSs modified separators exhibit excellent sulfur utilization, superb rate performance (656 mAh g^-1 at 5.0 C), and low-capacity decay rate of about 0.069% per cycle over 500 cycles at 1.0 C.