Amorphous carbon/graphite coupled polyhedral microframe with fast electronic channel and enhanced ion storage for potassium ion batteries

Carbonaceous materials are well suitable for potassium-ion batteries (KIBs) anode due to the advantages of low cost and excellent K⁺ intercalation/deintercalation reversibility. Nevertheless, it is attractive but challenging to achieve satisfactory electrochemical performance in terms of rate, capacity and stability. Herein, N-doped amorphous carbon/graphite coupled polyhedral microframe (NCM) is successfully synthesized as an advanced anode for KIBs. The graphite acts as fast electronic channel while the amorphous carbon can host more K⁺ and accommodate the volume change, thus boosting its rate, capacity and stability. The von Mises stress distribution after K⁺ intercalation is also studied to demonstrate the optimization process of strain caused by the volume change through the finite element method. Along with the large interlayer spacing (0.368 nm), rich active sites and highly accessible surface, the NCM electrode exhibits high reversible capacity of 358.4 mAh g⁻¹ at 500 mA g⁻¹, outstanding rate property (272.2 mAh g⁻¹ at 1000 mA g⁻¹) and superb cycling performance (189.5 mAh g⁻¹ after 1800 cycles at 2000 mA g⁻¹). Moreover, a K-ion full cell is successfully assembled on the basis of potassium Prussian blue (KPB)/NCM, exhibiting large energy density (177.6 Wh kg⁻¹) and good cycling stability.