Polyaniline-Derived Carbon Heterostructure as Redox Mediator of Li2S Oxidation and Polysulfide Immobilizer for High-Performance Lithium–Sulfur Cathode

The merit of high energy density endows the lithium sulfide (Li2S)-based lithium–sulfur batteries (LSBs) as a promising candidate for next-generation energy storage batteries. In this work, Li2S is chemically anchored onto the surface of two-dimensional graphene oxide (GO), which is then tangled and connected by one-dimensional carbon nanotube (CNT) to promote electron transfer, and finally further embedded with PANI-derived carbon (PDC) to suppress a polysulfide shuttle. The deliberately designed carbon matrix offers a fast electron and ion transfer route, suitable surface area, void volume, and pore size for redox reactions and polysulfide confinement. Furthermore, PDC could synergistically immobilize polysulfides inside the cathode by means of chemisorption so as to restrain the shuttle effect in LSBs. Last but not least, PDC with a quinone-based structure could function as a redox mediator (RM) to facilitate Li2S oxidation with minimized polarization. Benefited from the aforementioned advantages, the as-fabricated Li2S-GO/CNT/PDC composite, which is coupled with a lithium metal as the anode, delivers initially a high specific capacity of 925 mAh g–1 at 0.1 C and good retention capability of 550 mAh g–1 after 400 cycles at 2 C. Therefore, the good electrochemical behavior of the Li2S-GO/CNT/PDC composite suggests its promising prospects for the commercial application of LSBs in high-energy storage devices.