Insight into a Nitrogen-Doping Mechanism in a Hard-Carbon-Microsphere Anode Material for the Long-Term Cycling of Potassium-Ion Batteries

Abstract

To investigate the alternatives to lithium-ion batteries, potassium-ion batteries have attracted considerable interest due to the cost-efficiency of potassium resources and the relatively lower standard redox potential of K+/K. Among various alternative anode materials, hard carbon has the advantages of extensive resources, low cost, and environmental protection. In the present study, we synthesize a nitrogen-doping hard-carbon-microsphere (N-SHC) material as an anode for potassium-ion batteries. N-SHC delivers a high reversible capacity of 248 mAh g−1 and a promoted rate performance (93 mAh g−1 at 2 A g−1). Additionally, the nitrogen-doping N-SHC material also exhibits superior cycling long-term stability, where the N-SHC electrode maintains a high reversible capacity at 200 mAh g−1 with a capacity retention of 81% after 600 cycles. DFT calculations assess the change in K ions’ absorption energy and diffusion barriers at different N-doping effects. Compared with an original hard-carbon material, pyridinic-N and pyrrolic-N defects introduced by N-doping display a positive effect on both K ions’ absorption and diffusion.

Microwave-Mediated Stabilization and Carbonization of Polyacrylonitrile/Super-P Composite: Carbon Anodes with High Nitrogen Content for Lithium Ion Batteries

“…The larger capacities in the sloping region were due to the higher N atomic content and increased surface area (Figures b,S6). − ,, More pyridinic-N and graphitic-N in M1000W resulted in the exposure of more active sites for Li ions and enhanced electronic conductivity. − Therefore, facile redox reactions could be achieved, particularly at high current densities. The capacity increase in the plateau region is influenced by the larger crystallite size, which improves electronic and ionic transport. , The M1000W demonstrated an initial Coulombic efficiency (ICE) of 48.6%, whereas the T1000°C displayed an ICE of 52.4%.…”

“…The larger capacities in the sloping region were due to the higher N atomic content and increased surface area (Figures 4b,S6). [29][30][31]60,61 More pyridinic-N and graphitic-N in M1000W resulted in the exposure of more active sites for Li ions and enhanced electronic conductivity. 29−34 Therefore, facile redox reactions could be achieved, particularly at high current densities.…”

“…Carbon materials produced via microwave heating exhibited remarkable advantages over those produced via thermal convection, in terms of their reversible capacities and rate performance. The superior performance of microwave-heated carbon can be attributed to its high nitrogen content, which provides additional active sites for Li ion adsorption and enhanced electron transport. − Overall, it can be concluded that microwave carbonization represents a promising strategy for the production of carbon materials with enhanced electrochemical properties for LIBs and other next-generation batteries.…”

“…Moreover, the conformations of the nitrogen atoms were distinctly different. Pyridinic nitrogen is known to facilitate the efficient transport of Li ions by providing stable active sites for Li ions, and graphitic nitrogen enhances electronic conductivity. − Finally, the electrochemical properties of microwave-heated carbon materials were assessed to investigate their suitability as anode materials. Carbon materials produced via microwave heating exhibited remarkable advantages over those produced via thermal convection, in terms of their reversible capacities and rate performance.…”

Hard carbons: potential anode materials for potassium ion batteries and their current bottleneck

“…There are many kinds of singleatom doping, and different heteroatoms have various points to improve the electrochemical properties. At present, N-doping, 93,94 O-doping, 41,95 and S-doping 79 are the most common strategies to ameliorate the overall quality by increasing the active sites, adjusting the conductivity and enlarging the layer spacing.…”