Porous niobium carbide as promising anode for high performance lithium-ions batteries via cost-effective processing

Abstract

Porous niobium carbide (NbC) anode material was successfully synthesized for the first time via solid state carbothermic reduction of mechanically activated lithium niobium tartarate (LNT)/carbon black (C) mixture followed by acid leaching of embedded lithium in the structure. The synthesis process was systematically monitored by thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. The noticeable changes in the lattice parameters, cell volumes and crystallite sizes of both Li-embedded NbC (Li@NbC) and NbC samples could be assigned to the lattice defects created as a result of lithium atoms existence in the crystal structure of NbC. The surface morphology and chemical composition of niobium carbide samples before and after removal of lithium were sufficiently investigated by field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The total porosity of the prepared NbC sample was significantly increased from 64% before acid leaching to 76% after acid leaching. The assembled Li-ion battery from the obtained nanoporous NbC electrode delivered initial specific discharge capacity of about 400 mA h g−1 upon cycling at 100 mA g−1 and retained high specific capacity of about 107 mA h g−1 after 200 cycles. The enhanced reversibility and long cycle life of the developed nanoporous NbC anodes was confirmed by the reduced charge transfer resistance and high diffusion coefficient of Li+ ions after 150 cycles. The rate capability performance tests at different current densities 50, 150, 300 and 50 mA g−1 for nanoporous NbC anode showed excellent cyclic stability with high capacity retention of about 90% of its original capacity at 50 mA g−1.