Design of reduced graphene oxide coating carbon sub-microspheres hierarchical nanostructure for ultra-stable potassium storage performance

The development of high-performance carbon-based anode materials is still a significant challenge for K-ion storage. In our work, we designed reduced graphene oxide coating carbon sub-microspheres hierarchical nanostructure (CS@RGO) hierarchical nanostructure via a simple freeze-drying and subsequent pyrolysis as anode for K-ion batteries (KIBs), which presented an excellent electrochemical performance for K-ion storage, with a reversible specific capacity of 295 mAh g⁻¹ after 100 cycles at 100 mAh g⁻¹. Even at a high current density of 1 A g⁻¹, our CS@RGO still achieves ultra-stable K-ion storage of 200 mAh g⁻¹ at 1 A g⁻¹ after 5000 cycles almost without capacity fade. According to the galvanostatic intermittent titration technique result, the CS@RGO hybrid receives a high average diffusion coefficient of 7.35 × 10⁻⁸ cm² s⁻¹, contributing to the rapid penetration of K-ion, which facilitates the enhancement of electrochemical performance for KIBs. Besides, we also use Raman spectra to investigate the electrochemical behavior of our CS@RGO hybrid for K-ion storage and confirm the reaction process. We believe that our work will offer the opportunity to enable ultra-stable carbon-based materials by the structure design in the K-ion battery field.