Constructing tunable core-shell Co5Ge3@Co nanoparticles on reduced graphene oxide by an interfacial bonding promoted Kirkendall effect for high lithium storage performances

Although electrocatalysis conversion is effective in boosting lithium storage performances of Ge anodes, the electrocatalysts with spatially arranged structures and diverse functions are rarely reported. Herein, a novel interfacial bonding promoted Kirkendall effect is adopted to regulate interfacial bonding for constructing tunable core-shell Co5Ge3@Co nanoparticles on reduced graphene oxide (RGO) sheets via hydrothermal synthesis followed by thermal annealing. The Co shell thickness of Co5Ge3@Co could be tuned by varying the interfacial bonding between Co5Ge3@Co and RGO, which promotes the Kirkendall effect during the thermal annealing process. The spatially arranged Co components exhibit diverse functions to boost electrochemical performances of Ge. Both the Co core and the Co shell restrict significantly the volume change of the inner Ge component and enhance the electronic conductivity. Furthermore, the Co core as an electrocatalyst makes for the reversible conversion from GeO2 to Ge to Li4.4Ge, while the Co shell and the partial Co core are involved in the redox reactions from Co to Co2+/Co3+. Consequently, an optimal Co5Ge3@Co/RGO hybrid delivers an enhanced capacity of 1106 mA h g 1 after 100 cycles at 0.1 A g(-1). It also exhibits excellent long cycling performances with the capacities of 864 and 576 mA h g(-1) even after 500 cycles at 0.5 and 1 A g(-1), respectively. Clearly, the construction of tunable spatially arranged structures and diverse functions of electrocatalysts by the interfacial bonding promoted Kirkendall effect is an efficient methodology for highly boosting lithium storage performances of Ge-based anodes.