Ge nanograin-enhanced Si/C composite anodes: anchored interfaces for rapid electron and ion conduction

Abstract

Silicon (Si) anodes offer exceptionally high theoretical capacities for lithium-ion batteries. However, severe volume changes, low intrinsic conductivity, and fragile Si/C interfaces still hamper their practical application. To address these challenges, we developed a germanium-decorated silicon/carbon composite (ACGS@C) via chemical vapor deposition of Si into a porous carbon scaffold, concurrently introducing just 2 wt% Ge nanograins at the Si/C interface. These Ge nanograins not only build continuous electron/ion pathways but also chemically anchor Si, thus buffering expansion and mitigating interfacial degradation. Benefiting from the dual-function design, the ACGS@C-2 electrode exhibits a high initial reversible capacity of 1986.2 mA h g⁻¹ with an initial coulombic efficiency of 87.4%. Moreover, it delivers a specific capacity of 626 mA h g⁻¹ at 3.4 A g⁻¹ and retains 80% of its capacity after 270 cycles. This trace-Ge interfacial engineering strategy offers a scalable route to unlock the full potential of Si anodes without compromising energy density, rate capability, or cycling stability.