Defect-rich N/O-co-doped porous carbon frameworks as anodes for superior potassium and sodium-ion batteries

Carbon with its high electrical conductivity, excellent chemical stability, and structure ability is the most promising anode material for sodium and potassium ion batteries. We developed a defect-rich porous carbon framework (DRPCF) built with N/O-co-doped mesoporous nanosheets and containing many defects using porous g-C₃N₄ (PCN) and dopamine (DA) as raw materials. We prepared samples with PCN/DA mass ratios of 1/1, 2/1 and 3/1 and found that the one with a mass ratio of 2/1 and a carbonization temperature of 700 °C in an Ar atmosphere (DRPCF-2/1-700), had a large specific surface area with an enormous pore volume and a large number of N/O heteroatom active defect sites. Because of this, it had the best pseudocapacitive sodium and potassium ion storage performance. A half battery of Na//DRPCF-2/1-700 maintained a capacity of 328.2 mAh g⁻¹ after being cycled at 1 A g⁻¹ for 900 cycles, and a half battery of K//DRPC-2/1-700 maintained a capacity of 321.5 mAh g⁻¹ after being cycled at 1 A g⁻¹ for 1 200 cycles. The rate capability and cycling stability achieved by DRPCF-2/1-700 outperforms most reported carbon materials. Finally, ex-situ Raman spectroscopy analysis result confirms that the filling and removing of K⁺ and Na⁺ from the electrochemically active defects are responsible for the high capacity, superior rate and cycling performance of the DRPCF-2/1-700 sample.