Regulation of solid–electrolyte interphase formation via a Li3PO4 artificial layer for ultra-stable germanium anodes†

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 a Ge anode to protect it from pulverization. Through simple impregnation and subsequent annealing methods, lithiated phytate (PL) simultaneously converts to Li₃PO₄ and a 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 highly reversible alloying and de-alloying processes for the Li₃PO₄/C modified Ge anode. As a result, the as-designed Ge anode shows a high specific reversible capacity (1255.5 mA h g⁻¹), excellent capacity retention (more than 96% of the reversible capacity is retained from the 2^nd to the 600^th cycle), and ultra-high-rate performance (more than 1200.0 mA h g⁻¹ at 5.0 A g⁻¹), which outperforms previous results. This work provides a guide to the interfacial design of alloy-type anodes for next-generation battery applications.