"Pulverization-Reaggregation"-induced in situ pore expansion in carbon for fast potassium storage

The dominant microspores in conventional porous carbon materials restrict the fast diffusion kinetics of K+ with a large radius and thus lower the rate performance. Therefore, precisely increasing the pore size of carbon materials is essential but challenging for fast potassium storage. Herein, a general pore expansion strategy in carbon is realized via the in situ pulverization-reaggregation of basic carbonates with pitch as the carbon precursor. This strategy can be successfully applied to basic magnesium carbonate, basic zinc carbonate, basic nickel carbonate and basic cupric carbonate. Taking pitch/basic magnesium carbonate as an example, the flake-like basic magnesium carbonate in situ pulverized into nanoparticles during annealing, serving as s self-template to introduce pores into carbon nanosheets (CNSs). Then the nanoparticles reaggregated during further high-temperature annealing to etch the carbon matrix to induce pore expansion from 5.0 to 9.3 nm. Benefiting from the in situ pore expansion strategy, CNS-1100 possesses both rich defect sites and fast K+ diffusion kinetics, leading to a high reversible capacity (402 mA h g(-1) at 0.1 A g(-1) after 50 cycles) and high rate (217 mA h g(-1) at 1 A g(-1)). This work provides a powerful design for pore engineering and offers mechanism insights for fast potassium storage in carbon materials.