Mesoporous Nb2O5 microspheres with filled and yolk-shell structure as anode materials for lithium-ion batteries

Abstract

Nb2O5 materials based on intercalation reactions have been extensively studied as anode materials for lithium-ion batteries. Mesoporous Nb2O5 microspheres with narrow size distribution are the ideal structure for achieving a high volumetric capacity. Mesoporous filled- and yolk-shell-structured (reported for the first time) Nb2O5 microspheres are synthesized using a highly porous carbon template. The NbSe3-C composite transforms into yolk-shell-structured Nb2O5 microspheres by a one-step oxidation process. The filled microspheres having ultrafine crystallite size and high mesopore volume show better cycling and rate performances than the yolk shell microspheres. The discharge capacity of the filled microspheres at a current density of 1 A g(-1) is 124 mA h g(-1) in the 5000th cycle, and the capacity retention in the second cycle is 76%. The discharge capacity of the filled microspheres decreases by approximately 26% from 171 mA h g(-1) to 127 mA h g(-1) when the current density increases from 0.5 A g(-1) to 10 A g(-1). Particularly, the volumetric capacity of the filled microspheres at a high current density of 10 A g(-1) is 2.3 times higher than that of the yolk-shell-structured microspheres (filled approximate to 11.5 mA h cc(-1) vs. yolk approximate to 4.9 mA h cc(-1)). (C) 2018 Elsevier B.V. All rights reserved.