Ultra-small and highly crystallized ZnFe2O4 nanoparticles within double graphene networks for super-long life lithium-ion batteries

To achieve high-performance lithiumion batteries (LIBs), tremendous efforts have been devoted to the design of multifunctional electrode materials with a short Li+ diffusion pathway, high electronic conduction, large electrode/electrolyte contact area and efficiency elastic buffer space to accommodate volume change during cycling. However, the design and synthesis of these versatile structures still remain a big challenge. Here, for the first time we present a novel strategy for spatial confinement of ultra-small and highly crystallized ZnFe2O4 nanoparticles (similar to 12 nm) within double graphene networks constructed by ultra-small graphene sheets (USGNs) and large graphene sheets (GNs). The interconnected double graphene networks can act as a "barrier" for spatially confined growth of ZnFe2O4 and as a "structural buffer" for enhanced cycling stability, as well as electrically conductive paths. As a result, the ZnFe2O4/USGN/GN exhibits a large reversible capacity of 1257 mA h g(-1) at 0.1 A g(-1), excellent rate capability (575 mA h g(-1) at 1 A g(-1)), and superior cycling stability (706 mA h g(-1) at 0.5 A g(-1) after 1000 cycles and 475 mA h g(-1) at 1 A g(-1) even after 2000 cycles). Our strategy can be further extended to the fabrication of other electrode materials for supercapacitors, fuel cells and metal-ion batteries.