Dual-Armor Architecture-Mediated Microstructural Engineering of Germanium Anode for Advanced Liquid- and Solid-State Batteries

Abstract

Germanium (Ge) is an attractive anode material for advanced lithium-ion batteries (LIBs) due to its high theoretical capacity, excellent Li⁺ diffusivity, and high electronic conductivity. However, its substantial volume variation and unstable solid electrolyte interphase (SEI) during cycling lead to rapid capacity decay. Here, a p-Ge/SiO₂/NC-2 composite with a dual-armor architecture is developed through a rational pore-filling and interface engineering strategy. This unique structure features a porous Ge skeleton with embedded SiO₂ microspheres and an outer N-doped carbon layer, forming a stable inner support and outer confinement system. The mechanical integrity is enhanced by the porous structure and the rigid SiO₂ particles, which collectively inhibit pore collapse and mitigate volume expansion. Meanwhile, the N-doped carbon layer not only facilitates rapid charge transfer but also promotes the formation of a stable SEI enriched with LiF and Li₃N in liquid electrolyte systems. Finite element simulation further verifies that this synergistic dual-armor design enables low stress strain and high structural stability during cycling. As a result, the composite anode demonstrates exceptional lithium storage performance, achieving a high capacity retention of 94.4% after 250 cycles at 0.5 C in the LFP||p-Ge/SiO₂/NC-2 full cells. Notably, the p-Ge/SiO₂/NC-2||LPSC||Li all-solid-state lithium-ion batteries (ASSLIBs) with a sulfide solid electrolyte maintain stable cycling, delivering a specific capacity of 449 mAh g⁻¹ at 0.5 A g⁻¹. This work highlights the crucial role of rational structural design in advancing Ge-based anodes for high-performance energy storage systems.