Engineering vacancy-defect atomic Ni sites via biowaste valorisation for high-power kinetics in lithium-sulfur batteries

Lithium–sulfur (Li–S) batteries attracted much attention in the field of energy storage due to its outstanding theoretical energy density and eco-friendly materials. Nevertheless, the practical application of Li–S batteries is severely compromised by the rampant shuttle effect of soluble Li polysulfides (LiPSs) and sluggish kinetics of conversion under high sulfur loading (>5 mg cm‒2). Herein, we designed the vacancy-defect atomic Ni active sites on hierarchical porous ultrathin nanocarbon (named as SACs-Ni-NC) derived from biowaste chitin to boost the kinetics of lithium-sulfur batteries under high sulfur loading (9.5 mg cm−2). As a result, the 1.5 mg cm−2 S loading on SACs-Ni-NC composite delivered initial specific capacity of 810 mA h g‒1 at 5.0 C and maintained 78.5% after 1000 cycles. Remarkably, when the sulfur loading was elevated to 9.5 mg cm‒2, an areal capacity of 6.96 mA h cm‒2 was achieved at 2.0 C with the E/S ratio of 3.9 µL mg‒1 and stable for 200 cycles. The electrochemical tests and DFT calculations showed that the vacancy-defect atomic Ni sites not only afforded strong chemisorption for LiPSs but also synergistically promoted the redox kinetics process, demonstrating the superior prospect in developing practical Li−S batteries.