Embedded into Graphene Ge Nanoparticles Highly Dispersed on Vertically Aligned Graphene with Excellent Electrochemical Performance for Lithium Storage

Decreasing particle size has always been reported to be an efficient way to improve cyclability of Li-alloying based LIBs. However, nanoparticles (NPs) tend to agglomerate and evolve into lumps, which in turn limits the cycling performance. In this report, we prepared a unique nanostructure, graphene-coated Ge NPs are highly dispersed on vertically aligned graphene (Ge@graphene/VAGN), to avoid particle agglomeration and pulverization. Remarkable structure stability of the sample leads to excellent cycling stability. Upon cycling, the anode exhibits a high capacity of 1014 mAh g^–1, with nearly no capacity loss in 90 cycles. Rate performance shows that even at the high current density of 13 A g^–1, the anode could still deliver a higher capacity than that of graphite

All-Solid-State Symmetric Supercapacitor Based on Co₃O₄ Nanoparticles on Vertically Aligned Graphene

We have synthesized the hybrid supercapacitor electrode of Co₃O₄ nanoparticles on vertically aligned graphene nanosheets (VAGNs) supported by carbon fabric. The VAGN served as an excellent backbone together with the carbon fabric, enhancing composites to a high specific capacitance of 3480 F/g, approaching the theoretical value (3560 F/g). A highly flexible all-solid-state symmetric supercapacitor device was fabricated by two pieces of our Co₃O₄/VAGN/carbon fabric hybrid electrode. The device is suitable for different bending angles and delivers a high capacitance (580 F/g), good cycling ability (86.2% capacitance retention after 20 000 cycles), high energy density (80 Wh/kg), and high power density (20 kW/kg at 27 Wh/kg). These excellent electrochemical performances, as a result of the particular structure of VAGN and the flexibility of the carbon fabric, suggest that these composites have an enormous potential in energy application

Germanium Nanowires-in-Graphite Tubes <i>via</i> Self-Catalyzed Synergetic Confined Growth and Shell-Splitting Enhanced Li-Storage Performance

Despite the high theoretical capacity, pure Ge has various difficulties such as significant volume expansion and electron and Li⁺ transfer problems, when applied as anode materials in lithium ion battery (LIB), for which the solution would finally rely on rational design like advanced structures and available hybrid. Here in this work, we report a one-step synthesis of Ge nanowires-in-graphite tubes (GNIGTs) with the liquid Ge/C synergetic confined growth method. The structure exhibits impressing LIB behavior in terms of both cyclic stability and rate performance. We found the semiclosed graphite shell with thickness of ∼50 layers experience an interesting splitting process that was driven by electrolyte diffusion, which occurs before the Ge–Li alloying plateau begins. Two types of different splitting mechanism addressed as “inside-out”/zipper effect and “outside-in” dominate this process, which are resulted from the SEI layer growing longitudinally along the Ge–graphite interface and the lateral diffusion of Li⁺ across the shell, respectively. The former mechanism is the predominant way driving the initial shell to split, which behaves like a zipper with SEI layer as invisible puller. After repeated Li⁺ insertion/exaction, the GNIGTs configuration is finally reconstructed by forming Ge nanowires–thin graphite strip hybrid, both of which are in close contact, resulting in enormous enchantment to the electrons/Li⁺ transport. These features make the structures perform well as anode material in LIB. We believe both the progress in 1D assembly and the structure evolution of this Ge–C composite would contribute to the design of advanced LIB anode materials