Discovery of Dual‐Functional Amorphous Titanium Suboxide to Promote Polysulfide Adsorption and Regulate Sulfide Growth in Li–S Batteries

Lithium‐sulfur (Li–S) batteries are promising as next‐generation energy storage systems. Adsorbents for sulfide species are favorably applied to the cathode, but this substrate often results in a surface‐passivating lithium sulfide(Li(2)S) film with a strong adsorption of Li(2)S. Here, an amorphous titanium suboxide (a‐TiOx) is presented that strongly adsorbs lithium polysulfides (Li(2)S(x), x < 6) but relatively weakly adsorbs to Li(2)S. With these characteristics, the a‐TiO(x) achieves high conversion of Li(2)S(x) and high sulfur utilization accompanying the growth of particulate Li(2)S. The DFT calculations present a mechanism for particulate growth driven by the promoted diffusion and favorable clustering of Li(2)S. The a‐TiO(x)‐coated carbon nanotube‐assembled film (CNTF) cathode substrate cell achieves a high discharge capacity equivalent to 90% sulfur utilization at 0.2 C. The cell also delivers a high capacity of 850 mAh g(–1) even at the ultra‐high‐speed of 10 C and also exhibits high stability of capacity loss of 0.0226% per cycle up to 500 cycles. The a‐TiO(x)/CNTF is stacked to achieve a high loading of 7.5 mg S cm(–2), achieving a practical areal capacity of 10.1 mAh cm(–2).