In-situ chemical state transition of Ni nano-metal catalytic site promotes the reaction kinetics of lithium-sulfur battery

Abstract

Researchers have extensively explored the implementation of metal-based catalysts to address the slow conversion kinetics of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. However, the elucidation of foundational aspects, such as the in-situ transformation processes of monometallic catalysts within the Li-S battery reaction milieu, as well as the chemical states of resultant catalytic active centers, remains elusive. In this study, a flexible material (CBC/Ni) was prepared, consisting of a carbonized bacterial cellulose framework uniformly loaded with nickel nanoparticles, serving as a sulfur host. Through in-situ XRD and in-situ Raman studies, it was demonstrated that the nanoscale Ni catalyst in the S@CBC/Ni electrode undergoes an interaction with LiPSs during the operation of Li-S batteries, transforming into the chemical state of NiS2 and subsequently acting as a new active center to promote the conversion of LiPSs in the subsequent cycling process. Due to these advantageous characteristics, the S@CBC/Ni cathode delivers a high-rate capacity of 798.7 mAh/g at 2C, with an average capacity decay rate of only 0.064% over 500 cycles. This work provides a theoretical reference for the in-situ chemical transformation and functionality of nanoscale metal catalysts in the Li-S system.