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

Although GeO2 has a high theoretical capacity, its poor cyclic stability limits its application. In this work, amorphous GeO2/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 GeO2/C-24 composite electrode were 84 % for the 2nd to the 200th discharge, being significantly higher than that of the commercial GeO2 electrode (10 %). C doping changed the structure of GeO2 atomic bonds and made C and O combine preferentially, resulting in Li+ intercalating to the GeO2/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 GeO2 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.