A SnOx Quantum Dots Embedded Carbon Nanocage Network with Ultrahigh Li Storage Capacity.

Tin-based materials with high specific capacity have been studied as high-performance anodes for energy storage devices. Herein, a SnOx (x = 0, 1, 2) quantum dots@carbon hybrid is designed and prepared by a binary oxide-induced surface-targeted coating of ZIF-8 followed by pyrolysis approach, in which SnOx quantum dots (under 5 nm) are dispersed uniformly throughout the nitrogen-containing carbon nanocage. Each nanocage is cross-linked to form a highly conductive framework. The resulting SnOx@C hybrid exhibits a large BET surface area of 598 m2 g-1, high electrical conductivity, and excellent ion diffusion rate. When applied to LIBs, the SnOx@C reveals an ultrahigh reversible capacity of 1824 mAh g-1 at a current density of 0.2 A g-1, and superior capacities of 1408 and 850 mAh g-1 even at high rates of 2 and 5 A g-1, respectively. The full cell assembled using LiFePO4 as cathode exhibits the high energy density and power density of 335 Wh kg-1 and 575 W kg-1 at 1 C based on the total active mass of cathode and anode. Combined with in situ XRD analysis, the superior electrochemical performance can be attributed to the SnOx-ZnO-C asynchronous and united lithium storage mechanism, which is formed by the well-designed multifeatured construction composed of SnOx quantum dots, interconnected carbon network, and uniformly dispersed ZnO nanoparticles. Importantly, this designed synthesis can be extended for the fabrication of other electrode materials by simply changing the binary oxide precursor to obtain the desired active component or modulating the type of MOFs coating to achieve high-performance LIBs.