Hierarchical carbon nanotube/carbon black scaffolds as short- and long-range electron pathways with superior Li-ion storage performance

The combination of nanocarbon building blocks into hierarchical nanostructures is expected to bring good distribution of each element and even lead to formation of multifunctional composite cathodes with unexpected Li ion storage performance. The strategies toward fully demonstrating the potential of nanocarbon as three-dimensional (3D) conductive scaffolds for cathodes are highly required to broaden the application of nanocarbon in energy storage. Herein, hierarchical carbon nanotube/carbon black (CNT/CB) scaffolds were employed to promote the possible short- and long-range electron pathways in different scales within the LiFePO₄ cathode. With the construction of hierarchical CNT/CB conductive scaffolds, the LiFePO₄/C cathode exhibits enhanced Li storage performance and improved electrochemical kinetics. At a current density of 0.2 C, LiFePO₄/C cathode with such hierarchical CNT/CB networks exhibited reversible discharge capacity of 156.9 mAh g^-1 over 50 cycles. When the current density was increased to 1.2 C, a capacity of 119.1 mAh g^-1 was still preserved, and a capacity of 150.5 mAh g^-1 at 0.2 C rate was available after 1.2 C rate, indicating a high reversibility of the composite cathode. This strategy to hybridize CNTs and CBs into hierarchical scaffolds not only demonstrated its high efficiency to build LiFePO₄/C composite cathodes with excellent Li storage performance and good economy but also could be applied to supercapacitors, redox flow batteries, and Li/S and Li/O₂ batteries with improved energy storage performance.