Regulation of solid-electrolyte interphases formation via Li3PO4 artificial layer for ultra-stable germanium anodes

Abstract

Germanium (Ge) emerges as a promising candidate anode for building high energy density and fast-charging lithium-ion batteries. However, detrimental Ge particle pulverization caused by volume changes needs to be resolved. In this work, an artificial Li3PO4/C layer has been successfully developed on Ge anode to protect it from pulverization. Through a simple impregnation and subsequent annealing method, the lithiated phytate (PL) simultaneously converts to Li3PO4 and carbon composite coating layer. Theoretical calculations reveal that Li3PO4 can specifically adsorb fluoroethylene carbonate (FEC), which subsequently induces the formation of LiF-rich SEIs as demonstrated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses. In-situ X-ray diffraction (XRD) results also demonstrate a highly reversible alloying and de-alloying process for Li3PO4/C modified Ge anode. As a result, the as-designed Ge anode shows a high specific reversible capacity (1256 mAh g−1), excellent capacity retention (more than 96% of the reversible capacity is retained from the 2nd to the 600th cycle), and ultra-high-rate performance (more than 1200 mAh g−1 at 5.0 A g−1), which outperforms previous results. This work provides a guide to the interfacial design for alloy-type anodes for next-generation battery applications.