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.