A novel construction of Ti3C2@complete edge-nitrogen doped carbon spheres with excellent K-ion storage performance

Abstract

Edge nitrogen doping, including pyridinic and pyrrolic nitrogen, is an effective strategy to enhance the electrochemical performance of carbons for K-ion batteries owing to the abundant defective sites and lower K-ion adsorption energy than graphitic nitrogen. Nevertheless, due to the singleness of precursor and imprecise carbonization conditions, designing complete edge-nitrogen doped carbonaceous materials is still a grand challenge. Herein, we design a precise controlled pyrolysis strategy of the self-assembled Ti3C2 @melamine-E7 microcapsules (E7: one of the liquid crystals). This method leads to a complete edge nitrogen (100 at% edge nitrogen out of 15.07 at% nitrogen) doped Ti3C2-carbon double-shell hollow microsphere (NTC-HM). To date, such complete edge nitrogen doping level is the highest among the reported nitrogen doped carbon materials. We find that the NTC-HM, as anode for K-ion batteries, demonstrates an outstanding reversible capacity of 436.6 mAh/g of 0.1 A/g over 150 cycles and high capacity retention of 81.3% (Cycle 500/Cycle 3) under 1.0 A/g, which is among the best in all the excellent carbonaceous electrodes for K-ion batteries. Also, a full cell assembled perylenetetracarboxylic dianhydride (PTCDA) cathode and NTC-HM anode delivers a practical energy density of 126.9 Wh/kg under 0.2 A/g.