SiGe@Cu films as stable and high energy density anodes for lithium-ion microbatteries

Abstract

In this work, the deposition of stoichiometric SiGe alloy on Cu substrate by radio frequency (RF) magnetron sputtering was examined. The structure, morphology, and composition of the SiGe@Cu were identified by X-ray diffraction (XRD), Raman scattering, and scanning electron microscopy (SEM). The presence of Ge–Ge and Si–Si bonds at 254 and 477 cm−1 in Raman spectrum confirmed an amorphous morphology for SiGe films. To evaluate the electrochemical performance of SiGe@Cu anodes for lithium-ion batteries (LIBs), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were conducted in the potential range 0.05–1.2 V vs Li+/Li. The results of the CV test showed three reduction peaks in the first discharge cycle, and two oxidation peaks during the first charge cycle. These peaks proved that the reactions of lithiation and delithiation occurred on SiGe solid solution with formation of ternary LixSiyGey alloy. The voltage profiles of SiGe@Cu film anodes depicted lithiation and delithiation plateaus during GCD cycling. SiGe@Cu film anode exhibited a stable capacity during the 10 first GCD cycles. SEM-EDX analysis of cycled SiGe@Cu anode revealed that mechanical fractures and cracks were developed on the electrode surface disconnecting the particles from each other and leading to specific capacity fading. This problem can be overcome using carbon-based flexible current collectors. Graphical abstract[Figure not available: see fulltext.].