Ni/C Hierarchical Nanostructures with Ni Nanoparticles Highly Dispersed in N-Containing Carbon Nanosheets: Origin of Li Storage Capacity

Ni/C hierarchical composites, which consist of Ni nanoparticles highly dispersed in N-containing carbon nanosheets, were prepared via a facile, economical, and green route, and the electrochemical Li storage performance was investigated. On the basis of the available lithium storage mechanisms, Ni nanoparticles are inert to react with Li+ and contribute nothing to electrochemical Li storage. However, the composites exhibited an unexpected reversible capacity of 1051 mAh g(-1) after 30 cycles and 635 mAh g(-1) after 100 cycles at the current density of 200 mA g(-1). Such high reversible capacity cannot be simply ascribed to the Li insertion/extraction in carbon nanosheets. Instead, we proposed a possible origin of the reversible capacity, the electrochemical catalysis of Ni nanoparticles on the reversible formation/decomposition of some components in solid electrolyte interface films. These findings can further understand the role of transition-metal nanoparticles in lithium storage and open new doors for exploiting advanced materials for Li ion batteries and other energy-storage devices.