Breaking the Theoretical Capacity Limit of Fullerene Anode in Alkali‐Ion Batteries Through Two‐Dimensional Covalent Network Engineering

ABSTRACT

Carbon‐based anode materials offer compelling advantages for rechargeable ion batteries, and particularly fullerene C ₆₀ has a higher theoretical capacity of 446 mAh g ⁻¹ than the traditional graphite anode in lithium‐ion batteries (LIBs). However, its zero‐dimensional cage structure tends to spontaneously aggregate, and its alkali‐metal intercalated intermediate (fulleride) facilely dissolves in organic electrolytes, severely limiting its practical anode capacity and deteriorating recyclability. Herein, for the first time, we apply metal‐free two‐dimensional C ₆₀ covalent network (2D‐C ₆₀ ) with distinct bonding patterns, including tetragonal phase (TP‐2D‐C ₆₀ ) and hexagonal phase (HP‐2D‐C ₆₀ ) nanosheets, as novel anode materials for LIBs, achieving high anode capacity, breaking the theoretical limit of C ₆₀ molecule. TP‐2D‐C ₆₀ delivers a specific capacity of 522.0 mAh g ⁻¹ at 0.1 A g ⁻¹ , outperforming HP‐2D‐C ₆₀ (408.6 mAh g ⁻¹ ) and pristine C ₆₀ (3.4 mAh g ⁻¹ ). This phenomenon is rationalized by DFT calculations, revealing that TP‐2D‐C ₆₀ exhibits a higher density of Li‐ion binding sites and a lower Li‐ion migration barrier than HP‐2D‐C ₆₀ . To assess its universality across ion‐battery chemistries, we further demonstrate the application of TP‐2D‐C ₆₀ as an anode for sodium‐ion batteries (SIBs), achieving a high discharge capacity of 309.9 mAh g ⁻¹ at 0.1 A g ⁻¹ .