Nitrogen doping and graphitization tuning coupled hard carbon for superior potassium-ion storage

Hard carbon material is one of the most promising anode materials for potassium ion batteries（PIBs） due to its distinct disordered and non-expandable framework. However, the intrinsically disordered microarchitecture of hard carbon results in low electric conductivity and poor rate capability. Herein, nitrogendoped and partially graphitized hard carbons（NGHCs） derived from commercial coordination compound precursor-ethylenediaminetetraacetic acid（EDTA） disodium cobalt salt hydrate are designed and prepared as high-performance PIBs anode materials. By means of a facile annealing method, nitrogen elements and graphitic domains can be controllably introduced to NGHCs. The resulting NGHCs show structural merits of mesoporous construction, nitrogen doping and homogeneous graphitic domains, which ensures fast kinetics and electron transportation. Applying in anode for PIBs, NGHCs exhibit robust rate capability with high reversible capacity of 298.8 m Ah g;at 50 m A g;, and stable cycle stability of 137.6 mAh g;at 500 m A g;after 1000 cycles. Moreover, the ex situ Raman spectra reveal a mixture "adsorption–intercalation mechanism" for potassium storage of NGHCs. More importantly, full PIBs by pairing with perylenetetracarboxylic dianhydride（PTCDA） cathode demonstrate the promising potential of practical application. In terms of commercial precursor, facile synthesis and long cycle lifespan, NGHCs represent a brilliant prospect for practical large-scale applications.