Controlling the Placement of Spherical Nanoparticles in Electrically Driven Polymer Jets and its Application to Li‐Ion Battery Anodes

Abstract

Employing circumferentially uniform air flow through the sheath layer of the concentric coaxial nozzle, the gas-assisted electrospinning (GAES) utilizes both high electric field and controlled air flow to produce nanofibers. The ability to tailor the distribution of various nanofillers (1.85-12.92 vol% of spherical SiO and Si nanoparticles) in a polyvinyl alcohol jet is demonstrated by varying airflow rates in GAES. The distribution of nanofillers is measured from transmission electron microscopy and is analyzed using an image processing technique to perform the dispersion area analysis and obtain the most probable separation between nanoparticles using fast Fourier transform (FFT). The analysis in this study indicates an additional 350% improvement in dispersion area with the application of high but controlled airflow, and a 75 percent decrease in separation between nanoparticles from the FFT. The experiments in this study are in good agreement with a coarse-grained MD simulation prediction for a polymer nanocomposite system subjected to extensional deformation. Lastly, utilizing the sheath layer air flow in production of Li-battery anode material, a 680 mAh g improvement is observed in capacity for nanofibers spun via GAES compared to ES at the same Si NP loading, which is associated with better dispersion of the electrochemically active nanoparticles.

Strong Poly(Vinyl Alcohol) (PVA)/Bamboo Charcoal (BC) Nanocomposite Films with Particle Size Effect

“…With respect to PVA/BC nanocomposites in this study, A T = 624.81 and 527.41 m 2 g –1 are employed for NBCs and MBCs, respectively, based on BET surface areas listed in Table . In addition, R g = 10 nm for PVA is obtained from the previous literature …”

“…In addition, R g = 10 nm for PVA is obtained from the previous literature. 61 The value of kx can be changed for different nanocomposite systems due to the variation of interfacial interactions between polymer matrices and fillers. Besides, dynamic behavior of polymeric chains near attractive interfaces would be different from those bulk polymer phases, and the effect of attractive surfaces could be held for the distances larger than the radius of gyration for polymers.…”

“…Elastic moduli of polymer nanocomposites E 11 and E 22 in longitudinal and transverse directions can be experessed as where ν m is the Poisson's ratio of polymer matrices, which is 0.4 for PVA. 61 The A i (i = 1−5) are the functions of Eshelby's tensors and properties of matrices and fillers such as Young's modulus, Poisson's ratio, filler aspect ratio, and volume fraction. When nanofillers are prone to more random orientation, elastic modulus of nanocomposites can be further predicted by using the combination of laminate theory 65 and Mori-Tanaka model below:…”

Beyond the Single-Nozzle: Coaxial Electrospinning Enables Innovative Nanofiber Chemistries, Geometries, and Applications

“…However, when the researchers used a coaxial spinneret featuring an outer nozzle that blew air, continuous fibers were obtained. The additional elongational force from the air flow through the outer nozzle of a coaxial spinneret enabled Zhmayev et al 199 to overcome the cohesive forces to reduce the agglomeration of nanoparticles in polymeric fibers compared to those spun using a single-nozzle system. The fibers' potential as an anode in Li-ion batteries exhibited a 25% increase in current rate capacity compared to fibers obtained via single-nozzle electrospinning.…”

Multinozzle high efficiency electrospinning with the constraint of sheath gas

“…Zhmayev Y et al . used the coaxial sheath gas in the preparation of lithium‐ion battery anodes to increase the distribution uniformity of nanoparticles . The additional sheath gas is a novel way to promote the multineedle electrospinning, but there are few works that have been reported.…”