Abnormally High‐Lithium Storage in Pure Crystalline C<sub>60</sub> Nanoparticles
Linghong Yin, Jiung Cho, Su Jae Kim, Il Jeon, Injun Jeon, Mi‐Hee Park, Minjoon Park, Se‐Young Jeong, Dae-Hyung Lee, Dong‐Hwa Seo, Chae‐Ryong Cho
Abstract
Abstract Li + intercalates into a pure face‐centered‐cubic (fcc) C 60 structure instead of being adsorbed on a single C 60 molecule. This hinders the excess storage of Li ions in Li‐ion batteries, thereby limiting their applications. However, the associated electrochemical processes and mechanisms have not been investigated owing to the low electrochemical reactivity and poor crystallinity of the C 60 powder. Herein, a facile method for synthesizing pure fcc C 60 nanoparticles with uniform morphology and superior electrochemical performance in both half‐ and full‐cells is demonstrated using a 1 m LiPF 6 solution in ethylene carbonate/diethyl carbonate (1:1 vol%) with 10% fluoroethylene carbonate. The specific capacity of the C 60 nanoparticles during the second discharge reaches ≈750 mAh g −1 at 0.1 A g −1 , approximately twice that of graphite. Moreover, by applying in situ X‐ray diffraction, high‐resolution transmission electron microscopy, and first‐principles calculations, an abnormally high Li storage in a crystalline C 60 structure is proposed based on the vacant sites among the C 60 molecules, Li clusters at different sites, and structural changes during the discharge/charge process. The fcc of C 60 transforms tetragonal via orthorhombic Li x C 60 and back to the cubic phase during discharge. The presented results will facilitate the development of novel fullerene‐based anode materials for Li‐ion batteries.