Regeneration of Fe-Co gel-ball: Designing uniform heterojunction with double N-doped carbon towards high-rate energy-storage abilities

Abstract

Captured by high theoretical capacity and energy density, metal-sulfides have been regarded as strong candidates, but they still suffer from by polysulfides shuttling, volume swelling and slow kinetics. Herein, through the utilization of sol-gel precursors, the interesting heterostructure materials could be successfully prepared with multi-carbon layers, displaying uniform particle size and improved conductivities. Benefitting from the limitation and adsorption of carbon, the moving behaviors of polysulfides are effectively inhibited, accompanying with the alleviating volume expansion. More interestingly, the enhanced degree of interfacial redox reactions and electrochemical kinetics were noted, mainly resulted from the improved interfacial activities. As expected, used as Na-storage abilities, the capacity of optimized samples could reach up to 949.1 mAh g−1 at 0.2 A g−1, with remarkable coulombic efficiency 91.1 %. Moreover, the excellent capacity retention could be remained about 90.6 % even after 100 loops. Supported by DFT calculations, the adsorption energy of Na-atoms behaviors could be noted for heterostructure. Assisted by detailed kinetic analysis, their great charging capacity mainly originate from quickened interfacial ions/e− transfer rates and accelerated conversion-reaction kinetics. Given this, this work is expected to reveal the in-depth insight of energy-storage behaviors of hetero-structure, and offer effective designing strategies of sodium-ion storage systems.