Optimizing the Interlayer Spacing of Heteroatom-Doped Carbon Nanofibers toward Ultrahigh Potassium-Storage Performances

MOF-derived nitrogen-doped porous carbon nanofibers with interconnected channels for high-stability Li+/Na+ battery anodes

Heteroatom-doped porous carbon materials have been widely used as anode materials for Li-ion and Na-ion batteries, however, improving the specific capacity and long-term cycling stability of ion batteries remains a major challenge. Here, we report a facile based metal-organic framework (MOFs) strategy to synthesize nitrogen-doped porous carbon nanofibers (NCNFs) with a large number of interconnected channels that can increase the contact area between the material and the electrolyte, shorten the diffusion distance between Li⁺/Na⁺ and the electrolyte, and relieve the volume expansion of the electrode material during cycling; the doping of nitrogen atoms can improve the conductivity and increase the active sites of the carbon material, can also affect the microstructure and electron distribution of the electrode material, thereby improving the electrochemical performance of the material. As expected, the obtained NCNFs-800 exhibited excellent electrochemical performance with high reversible capacity (for Li⁺ battery anodes: 1237 mA h g^-1 at 100 mA g^-1 after 200 cycles, for Na⁺ battery anodes: 323 mA h g^-1 at 100 mA g^-1 after 150 cycles) and long-term cycling stability (for Li⁺ battery anodes: 635 mA h g^-1 at 2 A g^-1 after 5000 cycles, for Na⁺ battery anodes: 194 mA h g^-1 at 2 A g^-1 after 5000 cycles).

Coal-Based Semicoke-Derived Carbon Anode Materials with Tunable Microcrystalline Structure for Fast Lithium-Ion Storage

Fast charging capability is highly desired for new generation lithium-ion batteries used in consumer-grade electronic devices and electric vehicles. However, currently used anodes suffer from sluggish ion kinetics due to limited interlayer distance. Herein, the coal-based semicoke was chosen as precursor to prepare cost-effective carbon anodes with high-rate performance through a facile pyrolytic strategy. The evolution of microstructure and its effect on electrochemical performance are entirely studied. The results show that large number of short-ordered defective structures are generated due to the occurrence of turbostatic-like structures when pyrolyzed at 900 °C, which are propitious to large interlayer distance and developed porous structure. High accessible surface area and large interlayer spacing with short-ordered defective domains endow the sample treated at 900 °C under argon (A900) with accelerated ion dynamics and enhanced ion adsorption dominated surface-induced capacitive processes. As a result, A900 delivers high capacity (331.1 mAh g^-1 at 0.1 A g^-1) and long life expectancy (94.8% after 1000 cycles at 1 A g^-1) as well as good rate capability (153.2 mAh g^-1 at 5 A g^-1). This work opens a scalable avenue to fabricating cost-effective, high-rate, and long cycling life carbon anodes.