High-areal-capacity lithium storage of the Kirkendall effect-driven hollow hierarchical NiS_x nanoarchitecture

Three-dimensional (3-D) architectures can provide significant advantages as lithium ion microbattery electrodes by lengthening the vertical dimension. In addition, the nanoscale hierarchy and hollow properties are important factors for enhancing the performance. Here, we prepared a 3-D nickel sulfide nanoarchitecture via a facile low-temperature solution route. A Kirkendall effect-driven sulfidation of a 3-D nickel electrode was used to produce a hollow 3-D structure. Moreover, a nanoscale hierarchy can be formed with the use of highly concentrated sulfur species. The morphology, structure, and chemical composition of the 3-D nickel sulfide electrode are characterized in detail, and the formation mechanism is discussed based on a time-resolved study. The 3-D nickel sulfide electrodes show an outstanding areal capacity (1.5 mA h cm^-2 at a current rate of 0.5 mA cm^-2), making this electrode a potential electrode for 3-D lithium ion microbatteries with a large energy density. Moreover, this strategy is expected to provide a general fabrication method for transition metal sulfide nanoarchitectures.