Effect of Carbon Nanotube Loading on Electrical Properties of Electrospun Polyvinylidene Fluoride (PVDF) Fiber

Polyvinylidene fluoride (PVDF) is a high purity thermoplastic fluropolymer that use in the aircraft, electronics, and chemical industry. Carbon nanotube (CNTs) is made up of rolled up of graphite sheets, exhibits excellent chemical, thermal, mechanical properties, and large surface areas. PVDF fibers blended with CNTs were able to enhance the β-phase which contributes to piezoelectric properties. Electrospinning is the simplest and low-cost method to produce PVDF/CNT fibers by dissolving PVDF in solvent N, N-Dimethylformamide (DMF). 15wt% PVDF solution was used. CNT loading were varied at 0.0wt%, 0.35wt%, 0.80wt% and 1.00wt% with parameters of 20kV, tip-to-collector distance (TCD) 15cm and flow rate 1.0mLh-1. Scanning Electron Microscope (SEM), four-point probe and X-ray Diffraction (XRD) were used to determine the morphology and crystallinity of electrospun PVDF/CNT fibers. The SEM analysis concluded all fibers showed beaded structure due to low concentration of PVDF solution with insufficient ultrasonification and stirring, cause electrospraying and agglomeration. XRD and four-point probe analysis concluded PVDF/0.35wt%CNT showed the highest β-phase content with intense XRD peak and highest electrical conductivity. However, shift peak is observed among all fibres due to short electrospinning time leads to insufficient thickness of electrospun mat, which affects the mechanical properties of fibres and causes peak shift.

Microwave-Assisted Expanded Graphite as a Long Cyclic Cathode for the Lithium Dual-Ion Battery

Lithium metal (Li) has been recognized as a promising anode for most energy storage devices, owing to its high theoretical capacity. Nevertheless, Li anode present serious safety hazards and have a rapidly fading capacity, which limits its practical applications. Herein, a lithium-expanded graphite dual-ion battery (Li-EG DIB) was developed by combining a Li metal sheet as an anode with expanded graphite (EG) as a cathode. EG was produced by microwave (MW) photons energy (~1 × 10-5 eV) at different time durations (15, 30, 45, and 60 s) to allow moderate expansion between the graphite sheets and the removal of the surface functional groups that encourage the intercalation and de-intercalation of the ions; consequently, the capacity was improved. The MW-EG samples were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectrophotometry (FT-IR). The EG synthesized at 45 s in MW exhibited a high capacity and a stable and long cycling life. The charge capacity of the Li–EG-45 DIB after 500 cycles at 0.05 Ag-1 was 20.3 mAh g-1 in the voltage window of 2–5 V. It is worth noting that the EG-45 electrode showed ~100% capacity retention, even after the rate test.