The Origin of Strain Effects on Sulfur Redox Electrocatalyst for Lithium Sulfur Batteries

Abstract

Introducing strain is considered an effective strategy to enhance the catalytic activity of host material in lithium-sulfur batteries (LSB). However, the introduction of strain through chemical methods often inevitably leads to changes in chemical composition and phase structure, making it difficult to truly reveal the essence and root cause of catalytic activity enhancement. In this paper, strain into MoS2 is introduced through a simple heat treatment and quenching. Experimental research and theoretical analysis show that the strain raises parts of antibonding orbitals in Mo─S bonds above the Fermi level and weakens Li─S and S─S bonds, resulting in tight anchoring and accelerating the conversion for lithium polysulfides (LiPSs). The cells based on the MoS2 with high strain delivers an initial discharge specific capacity as high as 1265 mAh g−1 under 0.2 C and a low average capacity fading of 0.041% per cycle during 1500 cycles under 1 C. This research work deeply reveals the origin of strain effects in the reaction process of LSB, providing important design principles and references for the rational design of high-performance catalytic materials in the future.