Low-Cost Integrated Silicon-Carbon Anode Based on Si-Cu Bonds and Asphalt-Derived Carbon toward High-Performance Lithium-Ion Batteries

Silicon (Si)-carbon anode with a continuous carbon matrix can alleviate the volume expansion of Si. However, most carbon precursors need to be dissolved in organic solvents, which are toxic and expensive, and the particulate electrode materials are easily exfoliated from the current collector during cycling. Thus, it is highly desirable to develop a new green strategy for enhancing the performance of Si-carbon anodes. Here, we reported a low-cost and binder-free approach for fabricating an integrated Si@C-Cu anode with fast electronic transmission and excellent mechanical stability by employing a deep eutectic solvent as a green solvent and combining the Si@C materials with current collectors stably by generating strong Si-Cu bonds. The experimental results show that Si nanoparticles uniformly embed in the asphalt-derived carbon matrix to alleviate the volume expansion of Si, and Cu3Si alloy is generated between Si@C composites and Cu current collector which could significantly improve the electron transport rate and electrical contact. Density functional theory simulation demonstrates that the strong interaction between Cu and Si causes a significant shift of the p-band center in Si, resulting in the continuity of the total density of state at the Fermi level. Thus, the lithium-ion battery (LIB) based on the Si@C-Cu anode displays a high initial Coulombic efficiency of 84.8% and a specific capacitance of 2326 mAh g(-1) at 0.1 A g(-1). Moreover, it can deliver outstanding cycling stability by retaining 970 mAh g(-1) after 200 cycles at 1 A g(-1), which was about 11 times higher than that of the Si@C anode. This work provides a promising approach for application in high-performance Si/C anodes of LIBs.