Aerosol-assisted synthesis of 3D hybridized reduced graphene oxide-carbon nanotube composite microsphere with cobalt-iron selenide nanocrystal as anode materials for potassium-ion batteries

The combined strategies involving graphene and carbon nanotubes (CNTs) have garnered significant attention as a clever approach to address the inherent tendency of graphene to irreversibly aggregate due to strong van der Waals interactions. Recently, a notable method for crafting graphene-CNT composites has emerged, wherein CNTs are grown perpendicular to the graphene surface using catalysts like transition metal nanocrystals via chemical vapor deposition (CVD) techniques. In this study, we propose a novel anode material for potassium-ion batteries: a three-dimensionally hybridized composite microsphere comprising cobalt-iron selenide, reduced graphene oxide (rGO), and carbon nanotubes (CNTs). This novel material was introduced for the first time, employing both spray pyrolysis and CVD processes. The spray pyrolysis step was employed to generate crumpled rGO microspheres, effectively mitigating graphene's tendency to stack. The CNTs grown atop the rGO surface further acted as a barrier to prevent stacking. The bimetallic cobalt-iron nanocrystals enveloped in graphitic carbon were subsequently transformed into cobalt-iron selenide through a straightforward selenization process, enhancing its potential for potassium-ion storage. The resulting cobalt-iron selenide-rGO-CNT composite anode exhibited exceptional capacity and remarkable stability in cycling performance, outperforming the cobalt-iron selenide-rGO composite. To optimize the properties of these developed electrode materials, additional evaluations were undertaken to assess their characteristics based on the specific electrolyte type employed in potassium-ion batteries.