Enabling long cycle aluminum-sulfur batteries via structurally stable Co, N-doped graphene-CNTs covalently bonded hybrid

Abstract

Al-S batteries offer advantages such as high energy density, low cost, and good safety. However, they face challenges including poor sulfur conductivity, volume expansion, and slow kinetics of polysulfides, leading to rapid capacity decay and short cycle life. Therefore, the design of materials with high conductivity, capable of anchoring polysulfides, and structurally robust is crucial for enhancing the overall performance of Al-S batteries. To address these issues, we propose the construction of a structurally stable graphene-carbon nanotubes (CNTs) covalently bonded hybrid and a three-dimensional (3D) conductive framework catalyzed by Co active sites. The porous Co, N-doped graphene-carbon nanotubes (CoN-GC) hybrid with excellent mechanical properties provides sufficient space for high sulfur loading, alleviating sulfur volume expansion. Co plays a key role in rapidly transporting electrons, adsorbing, and catalyzing aluminum polysulfides. The Al-S battery using S@CoN-GC cycles over 1500 cycles at a current density of 300 mA·g−1, maintaining a specific capacity of 315 mAh·g−1, and retains 278 mAh·g−1 after 2000 cycles. Additionally, utilizing the outstanding mechanical properties of CoN-GC, a flexible Al-S microbattery was successfully fabricated, maintaining a capacity retention of 90 % after folding 1000 times. These research findings are expected to accelerate the study of multivalent metal-sulfur batteries and their practical applications in various scenarios.