Ce-Fe3O4@N-doped carbon derived from covalent organic framework for enhanced lithium storage

Fe3O4 has the potential to be an alternative material for the anode of lithium-ion batteries (LIBs) due to its high theoretical capacity, cheapness, and environmental friendliness. However, its inevitable volume expansion and poor Li+ storage dynamics due to small lattice spacing are disadvantages that severely limit its application. Here, Ce-Fe3O4 nanoparticles with large lattice spacing and porous structure were obtained by inserting Ce with a large radius into Fe3O4 lattice. Next, the Ce-Fe3O4 nanoparticles was used as the core for the in-situ growth of COFLZU1 to form Ce-Fe3O4@ COFLZU1. Finally, high-temperature calcination was carried out to obtain flexible nano-cages of nitrogen-doped porous carbon (NC)-covered Ce-Fe3O4 (Ce-Fe3O4@NC). Flexible NC nanocages not only accommodate the volume expansion of Fe3O4 but also increase the rate of Li+ transport and provide space for Li+ storage. The successful doping of Ce effectively increases the lattice spacing of Ce-Fe3O4, improving the space and efficiency of the embedded Li+. Compared with pure Fe3O4, Ce-Fe3O4 exhibits better performance when applied to the anode of LIBs. Ce-Fe3O4@NC exhibits best electrochemical performance during lithium storage, with capacities of 662.2 and 923.7 mAh g−1 after 500 cycles at current densities of 1000 mA g−1 and 100 mA g−1. This strategy of Ce doping combined with flexible NC cladding offers options for the preparation of other core-shell type carbon nanocomposites.