Carbon confined GeO2 hollow spheres for stable rechargeable Na ion batteries

Germanium (Ge) based nanomaterials are regarded as promising high-capacity anode materials for Na ion batteries, but suffer fast capacity fading problems caused by the alloying/de-alloying reactions of Na-Ge. Herein, we report a new method for preparing highly dispersed GeO2 by using molecular-level ionic liquids (ILs) as carbon sources. In the obtained GeO2@C composite material, GeO2 exhibits hollow spherical morphology and is uniformly distributed in the carbon matrix. The as-prepared GeO2@C exhibits improved Na ion storage performances including high reversible capacity (577 mA h g(-1) at 0.1C), rate property (270 mA h g(-1) at 3C), and high capacity retention (82.3% after 500 cycles). The improved electrochemical performance could be attributed to the unique nanostructure of GeO2@C, the synergistic effect between GeO2 hollow spheres and the carbon matrix ensures the anode material effectively alleviates the volume expansion and the particle agglomeration problems.

Automated summary

In this study, highly dispersed GeO2@C composite material was successfully prepared by using molecular-level ionic liquids (ILs) as carbon sources. The obtained GeO2@C exhibited improved Na ion storage performances, including high reversible capacity (577 mA h g(-1) at 0.1C), high capacity retention (82.3% after 500 cycles), and good rate property (270 mA h g(-1) at 3C). The unique nanostructure of GeO2@C, with hollow spheres of GeO2 uniformly distributed in the carbon matrix, contributed to the improved electrochemical performance by alleviating volume expansion and particle agglomeration problems.