GeO_x/reduced graphene oxide composite as an anode for li-ion batteries: Enhanced capacity via reversible utilization of Li₂O along with improved rate performance

A self-assembled GeO_x/reduced graphene oxide (GeO _x/RGO) composite, where GeO_x nanoparticles are grown directly on reduced graphene oxide sheets, is synthesized via a facile one-step reduction approach and studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy elemental mapping, and other techniques. Electrochemical evaluation indicates that incorporation of reduced graphene oxide enhances both the rate capability and reversible capacity of GeO_x, with the latter being due to the RGO enabling reversible utilization of Li₂O. The composite delivers a high reversible capacity of 1600 mAh g^-1 at a current density of 100 mA g^-1, and still maintains a capacity of 410 mAh g^-1 at a high current density of 20 A g^-1. Owing to the flexible reduced graphene oxide sheets enwrapping the GeO_x particles, the cycling stability of the composite is also improved significantly. To further demonstrate its feasibility in practical applications, the synthesized GeO_x/RGO composite anode is successfully paired with a high voltage LiNi_0.5Mn_1.5O₄ cathode to form a full cell, which shows good cycling and rate performance. A GeO_x/reduced graphene oxide (RGO) composite, where amorphous GeO_x (1.01 < x < 1.07) nanoparticles are in intimate contact with well-dispersed RGO sheets, is successfully synthesized via a facile one-step reduction approach. The introduction of conductive RGO sheets into germanium oxide is a simple but effective strategy for enhancing the reversible utilization of Li₂O and improving rate capability for Li⁺ storage in germanium oxides.