Microwave-Assisted Synthesis of Ge/GeO2-Reduced Graphene Oxide Nanocomposite with Enhanced Discharge Capacity for Lithium-Ion Batteries

Abstract

Germanium/germanium oxide nanoparticles with theoretically high discharge capacities of 1624 and 2152 mAh/g have attracted significant research interest for their potential application as anode materials in Li-ion batteries. However, these materials exhibit poor long-term performance due to the large volume change of 370% during charge/discharge cycles. In the present study, to overcome this shortcoming, a Ge/GeO2/graphene composite material was synthesized. Ge/GeO2 nanoparticles were trapped between matrices of graphene nanosheets to offset the volume expansion effect. Transmission electron microscopy images revealed that the Ge/GeO2 nanoparticles were distributed on the graphene nanosheets. Discharge/charge experiments were performed to evaluate the Li storage properties of the samples. The discharge capacity of the bare Ge/GeO2 nanoparticles in the first discharge cycle was considerably large; however, the value decreased rapidly with successive cycles. Conversely, the present Ge/GeO2/graphene composite exhibited superior cycling stability.

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

“…The capacity of the F-GeO 2 @C electrode remains 1300 mAh g –1 after 100 cycles with a Coulombic efficiency (CE) of 99.3%, which is much higher than that of the GeO 2 @C electrode (626 mAh g –1 ). F-GeO 2 @C also shows higher energy density than most previously reported carbonaceous GeO 2 composites, − which may be attributed to the effect of F-doping on the GeO 2 -based anodes. Figure d shows the reversible specific capacities of the F-GeO 2 @C electrode at a higher current density of 5 A g –1 .…”

“…Considerable efforts, such as the construction of the GeO 2 nanostructure and the integration of the carbon matrix to form hybrid composites, have been proposed to improve the electrochemical performance. − The various types of the carbon matrix not only enhance the electrical conductivity of the electrode but also accommodate the volume expansion and improve structural stability during cycling. − The capacities and cycling performance have been increased for these nanosized carbonaceous GeO 2 composites. However, because of irreversible generation of Li 2 O, low initial Coulombic efficiencies (ICEs) were often achieved in these GeO 2 -based anodes. − The addition of catalysts (Fe, Ge, etc.) to GeO 2 -based composites can activate effective reduction of partial Li 2 O.…”

Investigation into the Structural, Chemical and High Mechanical Reforms in B4C with Graphene Composite Material Substitution for Potential Shielding Frame Applications

“…A composite specimen manifested the maximum value of elastic modulus (84 MPa) with 0.6% of graphene nanoparticle content. The elastic modulus results clearly demonstrate the addition of graphene nanoparticles [29]. Retaining their high modulus and strong interfacial interaction with B4C, can efficiently and effectively reinforce the B4C matrix, which corresponds to the considerable increase in the modulus elasticity of composites.…”

Graphene, Graphene-Derivatives and Composites: Fundamentals, Synthesis Approaches to Applications

“…This method is known as the bottom-up technique which is also regarded as the construction technique. Chemical vapour deposition (CVD) [56,57], substrate-free gas-phase synthesis (SFGP) [58] epitaxial growth [59,60], template route [61] and total organic synthesis [62] are some of the exemplars of the construction method. The bottom-up technique has some advantages over the top-down approach as the former is capable of producing near to perfect graphene having a huge surface area.…”