Laser-synthesized metastable bismuth nanocrystals chemically bonded to reduced graphene oxide for excellent lithium storage

The poor interface contact between Bi nanoparticles and reduced graphene oxide (rGO) hinders the transfer of ions/electrons for lithium-ion batteries. We propose an innovative approach for fabricating ultrafine bismuth nanocrystals chemically bonded to reduced graphene oxide (Bi-rGO) by liquid-phase pulsed laser irradiation followed by a solvothermal reaction with graphene oxide. Metastable Bi nanocrystals synthesized by a laser (5.5 nm) are then combined with graphene oxide in a solvothermal process, undergoing lattice restructuring and shrinking to a record-small size of 2 nm, which is the smallest reported for Bi/C composites as far as we know. The Bi nanocrystals are uniformly anchored onto rGO nanosheets by strong Bi—O—C bonds, which not only suppress particle aggregation but also establish efficient ion/electron transport channels and alleviate volume expansion during lithiation. As a result, the Bi-rGO-2 anode consisting of 2 nm Bi nanocrystals has an exceptional reversible capacity of 586.7 mAh g−1 over 500 cycles under a current density of 100 mA·g−1, nearly doubling that of a Bulk Bi/rGO composite anode (318 mAh·g−1). Theoretical calculations confirm a higher binding energy between Bi and rGO at small particle sizes, while kinetic analysis reveals accelerated Li+ diffusion. This work provides a scalable way to design high-performance alloy anodes through metastable nanocrystal engineering and covalent interface coupling.