Hydrogen-Bonded Coordination Networks in Accordion-Like Copper Coordination Polymers Facilitate Efficient Catalytic Strategies in Lithium-Sulfur Batteries

Abstract

Lithium-sulfur batteries (LSBs) are attractive for electric vehicles due to their high theoretical capacity and low cost. However, they severely suffer from the“shuttle effect”, which causes capacity fading and self-discharge. Metal-organic frameworks (MOFs) have been proposed as an effective sulfur-loaded matrix material to mitigate this problem via providing sufficient catalytic sites for accelerating sulfur redox reactions (SRR). In this study, a novel accordion-like copper-based hydrogen-bonding coordination network matrix material is constructed with pyridine-2,4-dicarboxylic acid as the ligands, which the layered structure can effectively adsorbs LiPSs, thereby avoiding the loss of reactive active material. Besides that, the hydrogen-bonding coordination network can reduce the activation energy barrier of Li2S decomposition and the redox conversion rate between S8 and Li2S. It is revealed that the materials with ideal layered structure can facilitate SRR via providing Lewis acid-base interactions between Cu atoms and LiPSs. Electrochemical results in a high discharge capacity of 751.25 mAh·g-1 at a high current density of 2 C has been achieved and when returns to 0.2 C after 60 cycles, it can recover a high reversible capacity of 1093.63 mAh·g-1. It demonstrates that hydrogen bonding coordination network materials are a promising strategy for overcoming the challenges of LSBs and expanding their potential applications.

Keywords: copper coordination polymers, hydrogen bonding coordination networks, sulfur redox reactions, polysulfide conversion, rate capability