N-doped pinecone-based carbon with a hierarchical porous pie-like structure: a long-cycle-life anode material for potassium-ion batteries.

Pinecone-based biomass carbon (PC) is a potential anode material for potassium-ion batteries because it is abundant, cheap, renewable, and easy to obtain. However, because of inferior kinetics and the effects of volume expansion due to the large radius of the K+ ion, it does not meet commercial performance requirements. In this study, nitrogen-doped PC (NPC) was prepared by carbonization in molten ZnCl2 with urea as a nitrogen source. A strategy based on synergistic effects between N doping and ZnCl2 molten salt was used to produce a hierarchically porous pie-like NPC with abundant defects and active sites and an enlarged interlayer distance-properties that enhance K+ adsorption, promote K+ intercalation/diffusion, and reduce the effects of volume expansion. This NPC exhibited a high reversible capacity (283 mA h g-1 at 50 mA g-1) and superior rate performance and cyclic stability (110 mA h g-1 after 1000 cycles at 5 A g-1), demonstrating its potential for use in potassium-ion batteries.

Boron-Doped Pine-Cone Carbon With 3D Interconnected Porosity for Use as an Anode for Potassium-Ion Batteries With Long Life Cycle.

Potassium-ion batteries (KIBs) have received widespread attention as an alternative to lithium-ion batteries because of their low cost and abundance of potassium. However, the poor kinetic performance and severe volume changes during charging/discharging due to the large radius of potassium leading to low capacity and rapid decay. Therefore, development of anode materials with sufficient space and active sites for potassium ion deintercalation and desorption is necessary to ensure structural stability and good electrochemical activity. This study prepared boron-doped pine-cone carbon (BZPC) with 3D interconnected hierarchical porous in ZnCl2 molten-salt by calcination under high temperature. The hierarchical porous structure promoted the penetration of the electrolyte, improved charge-carrier diffusion, alleviated volume changes during cycling, and increased the number of micropores available for adsorbing potassium ions. In addition, due to B doping, the BZPC material possessed abundant defects and active centers, and a wide interlayer distance, which enhanced the adsorption of K ions and promoted their intercalation and diffusion. When used as the anode of a KIB, BZPC provided a high reversible capacity (223.8 mAh g-1 at 50 mA g-1), excellent rate performance, and cycling stability (115.9 mAh g-1 after 2000 cycles at 1 A g-1).

Selected-control synthesis of metal phosphonate nanoparticles and nanorods.

By surfactant-assisted methods, nanoscale Co(O3PC6H5).H2O species of different morphologies, namely, nanoparticles and nanorods, have been successfully synthesized and characterized. Upon removal of the organic part of the compound, peculiar Co2P2O7 porous nanorods formed.