Fluorine-Doped GeO₂@C Composite with Abundant Oxygen Vacancies for High-Capacity Lithium-Ion Batteries

Abstract

Rational engineering of nanostructured anode materials is important to develop lithium-ion batteries (LIBs). In this study, hierarchical composites of fluoridated carbonaceous GeO 2 (F-GeO 2 @C) with rich oxygen vacancies were prepared by a simple annealing method. It is found that F − ions not only exist in the carbon matrix but also replace O 2− of metallic oxides. The abundant introduced oxygen vacancies can provide more active sites and contribute to better electronic conductivity. Moreover, density functional theory (DFT) calculations confirm that Fdoping greatly changes the electronic structure of the GeO 2 composite, exhibiting interesting metallic behavior. Consequently, the F-GeO 2 @C anode shows an enhanced initial Coulombic efficiency (ICE) value of 71.6% and delivers excellent rate capability, much higher than most reported GeO 2 -based anodes. The enhancement of the electrochemical performance for F-GeO 2 @C is attributed to the hierarchical nanostructure and F-doping by increased reaction kinetics, reversibility, and cycling stability. Thus, such rational fabrication of the composite can motivate other high-performance germanium-based materials in LIBs.

In situ construction of oxygen vacancy-rich and fluorine-doped carbon-coated Ca2Fe2O5 for improved lithium storage performance

“…19 It is obvious that the strongest peaks of (141) of the CFO@FC composite migrated to a higher angle slightly in comparison with CFO@C and bare CFO, signifying the successful doping of small radius fluorine ions. 20,21 The scanning electron microscope (SEM) images (Fig. 1b and Fig.…”

“…The D and G characteristic bands located at B1351 cm À1 and B1593 cm À1 , respectively, correspond to the disordered carbon and the double-layered structural carbon, respectively. 19,28 Especially, the intensity ratio of the D band to G band (I D /I G = 0.90) for CFO@FC is higher than that of CFO@C (I D /I G = 0.82), which indicates the larger amount of defect in the fluorinated carbon (FC) layer, 21 while CFO nanoparticles show no significant D-band peak and G-band peak. This kind of F-doped carbon can possess more Li + storage sites than graphitic carbon as well as favors the increase of the electronic conductivity, 29 which can enhance the capacity of CFO@FC.…”

“…The doping-induced ample oxygen vacancies can generally ameliorate the anode material's conductivity and advance the charge transfer kinetics to enhance LIB's performance. 10,21,35,41 The electrochemical properties of the CFO@FC material by assembling coin-type cell LIBs were studied. For comparison, pristine CFO was also investigated.…”

“…The unusual performance of CFO@FC may be attributed to the F-doping-induced enrichment of oxygen vacancies to enhance its quick reaction kinetics and protect the structural integrity of the carbon layer structure. 12,21,51 The kinetic behavior of the as-fabricated CFO@FC electrode is investigated through the CV curves at scan rates from 0.1 to 1.0 mV s À1 in the potential range of 0.01-3 V (Fig. 4a).…”

Carbon confined GeO2 hollow spheres for stable rechargeable Na ion batteries

“…33 The widely used strategies to solve the problem of rapid capacity decay of GeO 2 are: (i) hybridize GeO 2 materials with carbonaceous materials (including graphene, carbon nanobers, etc. ); [34][35][36][37] (ii) use elemental (N, F, S) doped carbon to encapsulate GeO 2 and reasonably prepare porous and hollow nanostructures; [38][39][40][41] (iii) fabricate nanoscale GeO 2 /Ge materials and use the catalytic properties of Ge to enhance the cycle stability. 42,43 These synthetic methods are oen limited by high temperatures, complex equipment, or expensive precursors and hazardous solvents.…”