Key Takeaways & Executive Findings
- •• • Bi nanocrystals synthesized by pulsed laser irradiation (5.5 nm) undergo lattice restructuring during solvothermal reaction, shrinking to 2 nm—the smallest reported for Bi/C composites, enabling enhanced surface area and active sites for lithium storage. • • The Bi-rGO-2 anode achieves a reversible capacity of 586.7 mAh g−1 after 500 cycles at 100 mA g−1, nearly doubling the 318 mAh g−1 of Bulk Bi/rGO, demonstrating superior cycling stability and structural integrity. • • Strong Bi–O–C covalent bonds between Bi and rGO suppress particle aggregation and provide efficient ion/electron transport channels, mitigating volume expansion during alloying/dealloying, critical for long-term battery operation. • • Theoretical calculations confirm higher binding energy between Bi and rGO at smaller particle sizes, and kinetic analysis reveals accelerated Li+ diffusion, validating the design principle of metastable nanocrystal engineering for high-performance anodes.
Abstract
The poor interface contact between bismuth (Bi) nanoparticles and reduced graphene oxide (rGO) impedes ion/electron transfer in lithium-ion battery anodes. We report an innovative fabrication of ultrafine Bi nanocrystals chemically bonded to rGO (Bi-rGO) via liquid-phase pulsed laser irradiation followed by solvothermal reaction with graphene oxide. Metastable Bi nanocrystals synthesized by laser (5.5 nm) undergo lattice restructuring and shrink to a record-small size of 2 nm during solvothermal combination, the smallest reported for Bi/C composites. The Bi nanocrystals are uniformly anchored onto rGO nanosheets via strong Bi–O–C bonds, which suppress particle aggregation, establish efficient ion/electron transport channels, and alleviate volume expansion during lithiation. The Bi-rGO-2 anode, comprising 2 nm Bi nanocrystals, delivers an exceptional reversible capacity of 586.7 mAh g−1 over 500 cycles at 100 mA g−1, nearly doubling that of a Bulk Bi/rGO composite anode (318 mAh g−1). Theoretical calculations confirm higher binding energy between Bi and rGO at smaller particle sizes, while kinetic analysis reveals accelerated Li+ diffusion. This work provides a scalable route to high-performance alloy anodes through metastable nanocrystal engineering and covalent interface coupling.
1. Introduction
Commercial lithium-ion battery anodes based on graphite are approaching their theoretical capacity limit, while alloy-type anodes such as bismuth (Bi) offer high volumetric capacity (3800 mAh cm−3) and safe operating potential (0.5–0.75 V vs Li/Li+). However, Bi anodes suffer from severe volume expansion during lithiation and poor interfacial contact with conductive carbon matrices, leading to rapid capacity fade and limited rate capability. Conventional mechanical mixing or simple reduction methods fail to establish robust chemical bonding, resulting in inefficient ion/electron transfer and particle agglomeration.
This work addresses the bottleneck by employing liquid-phase pulsed laser irradiation to generate metastable Bi nanocrystals, which are subsequently chemically bonded to reduced graphene oxide (rGO) via a solvothermal reaction. The process yields ultrafine Bi nanocrystals (2 nm) uniformly anchored on rGO through strong Bi–O–C bonds, creating efficient transport channels and buffering volume changes. The resulting Bi-rGO-2 anode demonstrates exceptional reversible capacity (586.7 mAh g−1 after 500 cycles) and superior rate performance, offering a scalable strategy for high-performance alloy anodes.
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Su Yanxia, Zhang Xiuhai, Qiu Yuqian, Ban Miaohan, Zhang Jinbo, Li Chong, Xu Fei, Wang Hongqiang (2026). Laser-Synthesized Metastable Bismuth Nanocrystals Chemically Bonded to Reduced Graphene Oxide for Excellent Lithium Storage. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61068-2
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Frequently Asked Questions
What is the failure mechanism of Bi-based anodes under prolonged cycling, and how does the Bi-rGO architecture mitigate it?
Bi-based anodes suffer from severe volume expansion (up to ~200%) during lithiation, causing particle pulverization and loss of electrical contact. The Bi-rGO architecture, with 2 nm Bi nanocrystals strongly bonded to rGO via Bi–O–C bonds, buffers volume changes and maintains structural integrity, as evidenced by a reversible capacity of 586.7 mAh g−1 after 500 cycles at 100 mA g−1.
How does the particle size reduction to 2 nm affect the binding energy and electrochemical kinetics?
Theoretical calculations show that smaller Bi particles exhibit higher binding energy with rGO, enhancing interfacial stability. Kinetic analysis reveals accelerated Li+ diffusion due to shortened diffusion distances and abundant active sites, contributing to the high reversible capacity and rate capability.
What is the scalability of the laser irradiation and solvothermal synthesis for industrial production?
The liquid-phase pulsed laser irradiation is a scalable technique that can be adapted for continuous processing, and the solvothermal reaction is a standard industrial method. The process yields uniform 2 nm Bi nanocrystals, and the demonstrated performance suggests potential for scale-up, though cost and throughput need optimization.
How does the Bi-rGO-2 anode compare with commercial graphite anodes in terms of capacity and cycling stability?
Bi-rGO-2 delivers a reversible capacity of 586.7 mAh g−1 after 500 cycles, which is significantly higher than commercial graphite (~372 mAh g−1 theoretical). The cycling stability is exceptional, with capacity retention surpassing many advanced Bi-based anodes, making it a promising candidate for high-energy-density LIBs.
What is the role of the Bi–O–C chemical bond in the electrochemical performance?
The Bi–O–C covalent bond ensures strong interfacial contact between Bi and rGO, facilitating efficient electron transfer and ion transport. It also prevents particle aggregation and accommodates volume expansion, leading to enhanced cycling stability and rate capability, as confirmed by the superior performance of Bi-rGO-2.
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