In-situ synthesis of antimony nanoparticles encapsulated in nitrogen-doped porous carbon framework as high performance anode material for potassium-ion batteries

Abstract

Antimony anodes for potassium-ion batteries (PIBs) have garnered considerable scholarly interest owing to their high theoretical specific capacity and low operation potential for alloying with potassium. However, the large volume expansion during alloying in Sb anodes results in rapid capacity fading. Thus, in this study, we proposed a simple, one-step, cost-effective carbothermal reduction method to synthesize a nanostructured Sb encapsulated in an N-doped porous carbon framework (Sb@NPC). The optimized Sb@NPC-2 electrode, which was obtained using a Sb2O3:polyvinylpyrrolidone (PVP) molar ratio of 1:3, offered a high reversible capacity of 587.7 mAh g−1 at 100 mA g−1 over 50 cycles, 492 mAh g−1 at 200 mA g−1 over 100 cycles, and 360.8 mAh g−1 at 800 mA g−1 with a capacity retention of 75.7% over 500 cycles. Even at a high specific current of 4000 mA g−1, the electrode maintained a high reversible capacity of 385 mAh g−1, implying adequate rate capability. In addition, a full cell composed of Sb@NPC-2 anode and KFe[Fe(CN)6⋅xH2O] cathode exhibited excellent cycling stability by showing an exceptional reversible capacity of 432.5 mAh g−1, corresponding to a high capacity retention of 98% over 150 cycles. These excellent results were primarily attributed to the successful encapsulation of nanostructured Sb nanoparticles in the NPC, as well as the formation of a KF-rich solid electrolyte interphase film on the electrode surface. Furthermore, the simulation result based on density functional theory (DFT) revealed that N-doping in the porous carbon framework enhanced the electrical conductivity and Sb−K binding.