General Preparation of Three-Dimensional Porous Metal Oxide Foams Coated with Nitrogen-Doped Carbon for Enhanced Lithium Storage
journal contributionposted on 20.06.2016, 00:00 by Ke Lu, Jiantie Xu, Jintao Zhang, Bin Song, Houyi Ma
Porous metal oxide architectures coated with a thin layer of carbon are attractive materials for energy storage applications. Here, a series of porous metal oxide (e.g., vanadium oxides, molybdenum oxides, manganese oxides) foams with/without nitrogen-doped carbon (N–C) coating have been synthesized via a general surfactant-assisted template method, involving the formation of porous metal oxides coated with 1-hexadecylamine (HDA) and a subsequent thermal treatment. The presence of HDA is of importance for the formation of a porous structure, and the successive pyrolysis of such a nitrogen-containing surfactant generates nitrogen-doped carbon (N–C) coated on the surface of metal oxides, which also provides a facile way to adjust the valence states of metal oxides via the carbothermal reduction reaction. When used as electrode materials, the highly porous metal oxides with N–C coating exhibited enhanced performance for lithium ion storage, thanks to the unique 3D structures associated with highly porous structure and thin N–C coating. Typically, the porous metal oxides (V2O5, MoO3, MnO2) exhibited discharge capacities of 286, 303, and 463 mAh g–1 at current densities of 30 and 100 mA g–1, respectively. In contrast, the metal oxides with low valences and carbon coating (VO2@N–C, MoO2@N–C, and MnO@N–C) exhibited improved capacities of 461, 613, and 892 mAh g–1. The capacity retentions of about 87.5, 80.2, and 85.0% for VO2@N–C, MoO2@N–C, and MnO@N–C were achieved after 600 cycles, suggesting the acceptable cycling stability. The present strategy would provide general guidance for preparing porous metal oxide foams with enhanced lithium storage performances.