Graphene fibers(GFs)have demonstrated high strength,high electrical and thermal conductivity,mechanical flexibility,chemical stability,and good functionality,etc.at the macro-scale,and have been used in many different fields,particularly next-genera-tion wearable and flexible devices.This re-view provides an overview of recent advances in the fabrication of GFs,including wet spin-ning,confined hydrothermal synthesis,chem-ical vapor deposition,and other emerging techniques.Special emphasis is placed on the development of GF-based devices that con-vert solar,thermal,or moisture energy from the environment into electrical energy.The working principles,structural design,and performance of these devices are summarized and current challenges and prospects for their use in wearable energy systems are detailed.
Hard carbon (HC) derived from renewable biomass is a promising anode material for sodium-ion batteries (SIBs). However, controlling the structure of hard carbon so that it has a high energy density, favorable rate performance, and cycling stability is still a challenge. We propose a strategy to control the open pore structure of hard carbon derived from wood for sodium-200 Specific capacity/(mAh g-1) 150 100 50 0 33 mAh g-1 ion storage by the addition of sodium carbonate under carbonization at 1100 degrees C. The resulting HC has an increased interlayer spacing, and a more uniform open pore distribution (2-3 nm) with a high slope capacity, thereby enabling efficient sodium-ion transport and storage. The HC anode has a reversible capacity of 326 mAh g-1 at a current density of 30 mA g-1, and maintains a reversible capacity of 270 mAh g-1 at 1 A g-1 and a capacity of 68 mAh g-1 even at 10 A g-1 during rate performance tests. After 300 cycles, it retains 76.7% (207 mAh g-1) of its capacity at 1.0 A g-1. In situ Raman spectroscopy and the galvanostatic intermittent titration testing results reveal an adsorption-intercalation-filling sodium storage mechanism. This work provides a strategy to optimize the open pore structure of biomass derived hard carbon for high performance sodium ion storage.
