Enhanced performance of graphene-incorporated electrodes for solid-state lithium-sulfur batteries through facilitated ionic diffusion pathways

Abstract

Significant progress has been achieved in advancing all-solid-state lithium-sulfur batteries through the development of sulfide solid electrolytes. Nonetheless, a challenge lies in creating a percolated ion–electron conduction path with intimate contact between charge carriers throughout the cathode which is crucial for enhancing overall efficiency and addressing issues related to slow kinetics and impedance during battery operation. This study introduces a framework elucidating how the integration of graphene enhances electrode performance by refining ionic diffusion pathways. An idealized ionic diffusion pathway characterized by a continuous ionic network, facilitating minimum diffusion distances, is proposed. Through a parametric study substituting portions of ionic and electronic conductive agents with graphene, the impact on total ionic and electronic conductivity of positive electrodes was comprehended. The findings underscore the critical role of optimum graphene content, which fills the gaps between ionic conductive materials and creates the shortest diffusion paths for ions and electrons. While incorporating graphene into cathode electrodes is not novel, it is noteworthy that graphene, as a mixed ion–electron conductive material, significantly enhances ion mobility due to its 2D structure, addressing a crucial aspect of cathode performance. Upon achieving optimum composite formulation, empirical findings demonstrate substantial performance improvement, including a 17.7% increase in initial capacity and a remarkable 21% enhancement in capacity retention compared to electrodes without graphene.