Tailoring the Mn/Co ratio in electrospun Mn-Co oxide embedded-carbon nanofibers as cathode for high-performance zinc-ion batteries

Abstract

Manganese- and cobalt-based materials are considered promising cathode candidates for zinc-ion batteries (ZIBs) due to their environmental sustainability, high specific capacities, and the natural abundance of their constituent elements compared to those used in other metal-ion battery technologies. Nonetheless, their extensive utilization is impeded by sluggish kinetics and suboptimal durability. In addressing these challenges through nanostructure engineering, we present a novel approach by tailoring the Mn/Co ratio to synthesize MnCo₂O₄ (MCO) and CoMn₂O₄ (CMO) entrapped carbon nanofibers (CNFs) via the electrospinning technique and post-treatment. MCO-CNFs and CMO-CNFs exhibit excellent performance as zinc cathodes in ZIBs, achieving initial specific capacities of 501.94 mAh g⁻¹ and 399.32 mAh g⁻¹ at 0.05 A g⁻¹, respectively. CMO-CNFs demonstrate superior rate performance at high current densities, whereas MCO-CNFs exhibit better cycle stability. This complementary behavior highlights the tunable electrochemical characteristics enabled by Mn/Co ratio adjustment. Insightfully, the influence of the Mn/Co ratio on the electronic state of the elements and the electrochemical storage behavior of ZIBs during the charge/discharge process is convincingly explored using ex-situ techniques such as scanning electron microscopy and operando X-ray absorption near-edge structure, proving that MCO-CNFs are more stable and redox-reversible than CMO-CNFs.