The appearance of mechanical cracks originated from anisotropic expansion and shrinkage of electrode particles during Li+ de/intercalation is a major cause of the capacity fading in Li-ion batteries. Well-designed and controlled nanostructures of electrodes have shown a prominent prospect for solving this obstacle. Here, we report a novel and convenient strategy for the preparation of graphene nanoscroll wrapping Nb2O5 nanoparticles (denoted as T-Nb2O5/G). First, high energy ball milling is conducted to acquire softly agglomerated T-Nb2O5 nanoparticles owing to its spontaneous reduction of surface energy among these single particles. Then freeze-drying leads to the formation of graphene nanoscroll, which easily realizes the in situ wrapping over softly agglomerated T-Nb2O5 nanoparticles. Extended cycling tests demonstrate that such T-Nb2O5/G yields a high reversible specific capacity of 222 mA h g-1 over 700 cycles at 1C. The dominated surface capacitive insertion processes possessing favorable kinetics enable T-Nb2O5/G to exhibit excellent rate performance, which achieve a capacity of 110 mA h g-1 at 10C. A combined ex situ X-ray diffraction, scanning electron microscopy, and transmission electron microscopy investigation reveal that the long-term cycling stability of T-Nb2O5/G is attributed to the excellent structural stability of the electrode, in which the synergistic effect between the softly agglomerated T-Nb2O5 nanoparticles and graphene nanoscroll prevents the formation of mechanical cracks.
Keywords: Li-ion batteries; Nb2O5/graphene composite; graphene nanoscroll; intergranular crack; soft-agglomeration.