Steric-Hindrance Effect Induced Fabrication of Lightweight, Bi-Functional, and Easy-to-Infiltrate Hosts for 502 Wh kg^-1 Lithium-Sulfur Batteries.

Abstract

A promising strategy for constructing 500 Wh kg^-1 cell-level rechargeable lithium-sulfur batteries (LSBs) is developing hosts with ultralight weight to reduce nonactive mass, bi-functionality to ensure both efficient sulfur reactions and lithium plating under low N/P, and an easy-to-infiltrate architecture for full wetting with lean electrolyte. Edge-doped carbons, combining light weight and unique bi-functionality, are rare candidates as such hosts. However, their preparation, which generally involves increasing specific surface areas or forming micropores/mesopores, impairs host-wetting under lean electrolyte. Herein, a steric-hindrance-induced approach is pioneered to create abundant edge-doping-sites on an easy-to-infiltrate host of carbon nanofibers (CNF). Boron-containing carbon dots (BCDs) are elaborately utilized as heteroatom-introducing agents. Their organic nature facilitates uniform integration of graft-like BCD units, while their inorganic crystalline cores suppress graphitization of CNF precursors surrounding these graft-like units via steric-hindrance during carbonization, promoting bi-functional edge-B-doping sites formation. Such a host enables 2 Ah pouch-type LSBs to achieve an impressive energy density of 502 Wh kg^-1 with enhanced cyclic stability.