Three-dimensional carbon microclusters organized by hollow carbon nanospheres for stable Li metal anodes: enabling high packing density and low tortuosity via self-assembly

Recently, hollow carbon nanospheres (HCSs) have garnered significant attention as potential Li metal hosts owing to their unique large voids and ease of fabrication. However, similar to other nanoscale hosts, their practical performance is limited by inhomogeneous agglomeration, increased binder requirements, and high tortuosity within the electrode. To overcome these problems and high tortuosity within the electrode, this study introduces a pomegranate-like carbon microcluster composed of primary HCSs (P-CMs) as a novel Li metal host. This unique nanostructure can be easily prepared using the spray-drying technique, enabling its mass production. Comprehensive analyses with various tools demonstrate that compared with HCS hosts, the P-CM host requires a smaller amount of binder to fabricate a sufficiently robust and even surface electrode. Furthermore, owing to reduced tortuosity, the well-designed P-CM electrode can provide continuous and shortened pathways for electron/ion transport, accelerating the Li-ion transfer kinetics and prohibiting preferential Li plating at the upper region of the electrode. Due to these characteristics, Li metal can be effectively encapsulated in the large inner voids of the primary HCSs constituting the P-CM, thereby enhancing the electrochemical performance of P-CM hosts in Li metal batteries. Specifically, the Coulombic efficiency of the P-CM host can be maintained at 97% over 100 cycles, with a high Li deposition areal capacity of 3 mAh·cm⁻² and long cycle life (1000 h, 1 mA·cm⁻², and 1.0 mAh·cm⁻²). Furthermore, a full cell incorporating a LiFePO₄ cathode exhibits excellent cycle life.