In-Situ Ge/Zn2GeO4 Heterojunctions Coupled with a Rigid-Flexible TiO 2 /NC Dual Coating for High-Performance Lithium-Ion Battery Anodes

Abstract

Zinc germanate (Zn2GeO4) is a promising anode material to fulfill the requirements for high-performance lithium-ion batteries (LIBs). However, its practical application is hampered by intrinsic low electrical conductivity and substantial volume variation during cycling. Herein, a hierarchically structured porous composite (Ge/Zn2GeO4@TiO2@NC) is rationally designed and synthesized via a combined hydrothermal synthesis, liquid-phase coating, and a single-step hydrogen reduction process.This architecture integrates an in-situ formed Ge/Zn2GeO4 heterojunction, a rigid TiO2 shell, and a flexible N-doped carbon (NC) overlayer. The built-in electric field at the heterojunction interface enhances charge transport, while the porous structure accommodates volume changes. The dual coating of TiO2 and NC collectively suppresses electrode pulverization, improves conductivity, and stabilizes the electrode-electrolyte interface. When evaluated as an anode for LIBs, the Ge/Zn2GeO4@TiO2@NC composite delivers a high reversible capacity (1458.7 mAh g -1 at 1C), outstanding rate capability, and exceptional long-term cycling stability (87.4% capacity retention after 5000 cycles at a high current density of 10C).