Defect-Selectivity and "Order-in-Disorder" Engineering in Carbon for Durable and Fast Potassium Storage.

Abstract

Defect-rich carbon materials possess high gravimetric potassium storage capability due to the abundance of active sites, but their cyclic stability is limited because of the low reversibility of undesirable defects and the deteriorative conductivity. Herein, in situ defect-selectivity and order-in-disorder synergetic engineering in carbon via a self-template strategy is reported to boost the K⁺ -storage capacity, rate capability and cyclic stability simultaneously. The defect-sites are selectively tuned to realize abundant reversible carbon-vacancies with the sacrifice of poorly reversible heteroatom-defects through the persistent gas release during pyrolysis. Meanwhile, nanobubbles generated during the pyrolysis serve as self-templates to induce the surface atom rearrangement, thus in situ embedding nanographitic networks in the defective domains without serious phase separation, which greatly enhances the intrinsic conductivity. The synergetic structure ensures high concentration of reversible carbon-vacancies and fast charge-transfer kinetics simultaneously, leading to high reversible capacity (425 mAh g^-1 at 0.05 A g^-1 ), high-rate (237.4 mAh g^-1 at 1 A g^-1 ), and superior cyclic stability (90.4% capacity retention from cycle 10 to 400 at 0.1 A g^-1 ). This work provides a rational and facile strategy to realize the tradeoff between defect-sites and intrinsic conductivity, and gives deep insights into the mechanism of reversible potassium storage.