Highly synergistic electrocatalysis and confinement of covalently bonded heterostructures enable high-efficient-stable Li−S batteries

Li₂S, as a high-capacity Li-containing cathode, can avoid the use of metallic Li in batteries, so as to improve cycle-life and safety. However, intrinsic low electrical conductivity, high activation barrier and serious polysulfide dissolution of Li₂S limit its performance output. Here, we propose a chemical cyclization crosslinking strategy to construct a covalently bonded Li₂S−cyclized polyacrylonitrile (cPAN) heterostructure, aiming to facilitate fast Li₂S activation and electron/ion transport as well as high volumetric accommodation. The obtained structure features crystalline Li₂S wrapped by conformal cPAN layer via robust Li−N bonding, forming compact Li₂S@cPAN core-shell nanocomposite. Systematic studies demonstrate distinguished synergistic electrocatalysis and confinement on Li₂S, where the bridge-like heterostructure composed of strong and abundant Li−N bonds facilitates fast electron/ion transport and Li₂S dissociation, and the core-shell nanostructure with elastic and dense cPAN enhances volumetric efficiency for accommodating sulfur species. Owing to improvement on both electrocatalysis and domain effects, this cathode design enables promising electrochemical performance. An optimal Li₂S@cPAN cathode exhibits a dramatically reduced activation potential (2.7 V), a largely increased output capacity (730 mAh g⁻¹), and an obviously improved cycling stability (500 cycles). This Li₂S@cPAN cathode demonstrates the great application potential for high-efficient-stable Li−S batteries.