High capacity amorphous GeO2/C composite anodes for improved long cycle stability of lithium-ion batteries

Although GeO 2 has a high theoretical capacity, its poor cyclic stability limits its application. In this work, amorphous GeO 2 /C composite anode materials were prepared by hydrothermal and sintering methods to improve the long-term cycle stability of Ge based anodes. The reversible specific capacity of the anode was 1300 mAh g −1 after 200 stable cycles at a current density of 0.2 A g −1 , and it was 1002 mAh g −1 after 1000 long cycles at a high current density of 1 A g −1 . The capacity retention rates of the amorphous GeO 2 /C-24 composite electrode were 84 % for the 2nd to the 200th discharge, being significantly higher than that of the commercial GeO 2 electrode (10 %). C doping changed the structure of GeO 2 atomic bonds and made C and O combine preferentially, resulting in Li + intercalating to the GeO 2 /C interface and the increase in the number of lithiation reaction sites, Li + diffusion coefficient, lithium-storage capacity and electrode capacity. The volume expansion rate of GeO 2 was reduced from 12.84 % to 2.51 % by C doping, resulting in the high structure stability of the anode in long cycles for LIBs. The reason was the stress release effect of the amorphous C coating, and the formation of a stable and appropriate thickness of the SEI film.