Crystalline Layered Fullerene Network with Exceptionally High Density of Intercalated Alkali Ions

Fullerene network is an emergent two-dimensional carbon allotrope composed of covalently-bonded, hexagonally packed C ₆₀ molecules. Layer-by-layer assembly of fullerene network offers opportunities beyond the reach of existing materials for hosting unexplored intercalation chemistry, because of its hierarchical π-electron conjugation and abundant coordination sites. However, conventional strategies for creating such layered crystalline structure rely on cumbersome restacking, leading to limited yield and reproducibility. Herein, we demonstrate the topochemical synthesis of crystalline layered C ₆₀ network (LCNW) with a wide interlayer gap (9.2Å), exceeding twice the graphite interlayer distance. The electrochemical measurements indicate that every crystal unit of LCNW accommodates approximately 12 Li ⁺ , 3 Na ⁺ or 2 K ⁺ ions, respectively. The superdense storage of intercalated Li ⁺ /Na ⁺ (i.e. Li ₁₂ C ₆₀ and Na ₃ C ₆₀ ) ^{surpasses the theoretical density limit of state-of-the-art carbon materials (i.e. LiC ₆ and NaC ₁₈₆ ). These findings highlight the potential of LCNW as a new material platform for energy storage and other functional applications.}