Rational design of fly ash-based composites for sustainable lithium-ion battery anodes

Lithium-ion batteries (LIBs) have dominated the energy market for decades, but the sustainability considerations should be included when designing future electrode materials due to the complex preparation process and severe volume expansion of the current Si-based anode materials. As an atmospheric pollutant, Fly ash (FA) is worth considering as a potential source of silicon, whereas the conventional magnesiothermic reaction to extract silicon from FA for LIBs is complex, costly and energy consuming. Herein, FA is employed directly as “green” and advanced anode of LIBs after being anchored on the carbon micro-sheets (FA/C) via low cost and solvent-free approach. Owing to the remarkably enhanced electric conductivity and mechanical properties, the resulting battery delivers an excellent capacity of 688 mAh g⁻¹ at 0.1 A g⁻¹, ultrahigh capacity retention of 97.9% over 6000 cycles and effectively mitigated volume variation, outperforming many Si-based anodes reported. Remarkably, the full battery with LiFePO₄ cathode displays ideal rate capability and long-term durability, demonstrative of great potential in practical application. Moreover, this low cost, free of organic solvents, harsh acids and surfactants method can be extended to FA/graphite and FA/MXene composites, thus providing an insight for sustainable recycling of fly ash and construction of durable LIBs.