Thin-film solid-state batteries are attracting increased attention for their applications in electric mobility, microelectronics, and Internet of Things (IoT) devices, where compactness, high energy density, and enhanced safety are paramount. The development of advanced anode materials is crucial for improving battery performance and longevity within these systems. Among the various thin-film anode materials investigated, germanium (Ge) has emerged as particularly promising due to its high theoretical capacity and rapid lithium diffusion kinetics, which enable efficient charge storage and swift electrochemical reactions compared to many other thin-film anodes.
However, Ge-based electrodes experience significant volume fluctuations during lithiation and delithiation, leading to mechanical stress, particle fracture, and the development of an unstable solid electrolyte interface (SEI), which ultimately reduces cycle stability. This study explores a hybrid Ge–Cu thin-film structure produced via magnetron sputtering to address these limitations. The incorporation of copper enhances the electrical conductivity of the electrode and aids in accommodating mechanical strain within the germanium structure, thereby reducing interfacial resistance and mitigating structural degradation.
Material characterisation studies confirm that the Ge–Cu thin film exhibits improved conductivity and forms a more stable solid electrolyte interphase (SEI) layer compared to pristine Ge films. The Ge–Cu electrode demonstrates significantly enhanced electrochemical performance, maintaining high reversible capacity and robust capacity retention over extended cycling, whereas the pure Ge electrode experiences rapid deterioration.
The findings suggest that the construction of hybrid thin-film structures using germanium is an effective strategy to overcome the mechanical and electrochemical limitations of high-capacity anodes. This approach supports the development of reliable, high-efficiency thin-film solid-state batteries for next-generation energy storage applications.