Graphdiyne-like Porous Organic Framework as a Solid-Phase Sulfur Conversion Cathodic Host for Stable Li-S Batteries.

Abstract

As a unique branch of Li-S batteries, solid-phase sulfur conversion polymer cathodes have shown superior stability with fast ion-transfer kinetics and high discharge capacities owing to the mere existence of short-chain sulfur species during charging/discharging. However, representative compounds such as sulfurized polyacrylonitrile (SPAN) and polyaniline (SPANI) suffer from low sulfur contents and poor cycling performances under large current densities due to the sulfurization occurring only on polymers' surface. Here, a graphdiyne-like porous organic framework, denoted as GPOF, is synthesized and used as a host for enabling solid-phase sulfur conversion. Plenty of unsaturated bonds in GPOF provide sufficient reaction sites to bind sulfur chains, resulting in a high active sulfur content in the cathode. Moreover, the microporous GPOF possesses suitable cavities to accommodate the volume expansion, leading to favorable long-term cycling stability. As a result, the sulfurized GPOF cathode (SGPOF-320) displays outstanding electrochemical stability with negligible capacity decline after 250 cycles at 0.2 C with an average discharge capacity of 925 mA h g-1. Our work applies a facile procedure to produce sulfur conversion porous polymer cathodes, which could provide a proper way for exploring more suitable cathode materials for high-performance Li-S batteries.