Layer-by-layer self-assembled covalent triazine framework/electrical conductive polymer functional separator for Li-S battery

Lithium-sulfur (Li-S) battery is attracting intense attention due to its extremely high theoretical specific capacity and low cost. However, the dissolution and diffusion of lithium polysulfides (LiPS), as well as the insulating property of sulfur and its discharge products, limit the practical application of Li-S battery. In this work, we developed an ultralight functional separator (LBL-fseparator) with orderly structure and multifunctional properties through electrostatic layer-by-layer (LBL) self-assembly of positively charged poly(diallyl dimethyl ammonium chloride) (PDDA) wrapped covalent triazine framework (CTF) (CTF@PDDA) and negatively charged poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) to effectively retard LiPS shuttle and improve the utilization of active sulfur material. The CTF@PDDA as LiPS shuttle inhibiting layers displays strong LiPS-anchor ability through physical/chemical interaction as well as excellent electrolyte uptake capacity due to its large specific surface area and porous structure, while the PEDOT: PSS as the conductive layers improves electron transfer as well as excellent interface stabilizer and adhesion binder. It was demonstrated that the proposed LBL-fseparator assembled with general S-cathode and Li metal anode displays commendable cycling stability (0.052% capacity fade-rate per cycle over 1000 cycles at 1C), superb utilization of sulfur (90.7% at 0.1C and 59.2% at 2C), and enhanced protection ability of the Li metal. The excellent battery performance and easily mass-produced method provide a useful strategy for industrial-scale production.

Automated summary

In this study, an ultralight functional separator with an orderly structure and multifunctional properties was developed through electrostatic layer-by-layer self-assembly, aiming to effectively slow down the shuttle effect of lithium polysulfides and improve the utilization of active sulfur material. The separator demonstrated excellent battery performance with commendable cycling stability and enhanced protection ability of the Li metal, providing a useful strategy for industrial-scale production.