Designing a composite
separator that can withstand high temperature, deliver high capacity,
and offer fast charge–discharge capability is imperative for
developing a high-performance lithium-ion battery. Here, a series
of ceramic nanoparticle-coated nanofiber membranes, including Al2O3/poly(vinylidene fluoride) (PVDF), SiO2/PVDF, and Al2O3/SiO2/PVDF, were
prepared by melt-electrospinning and magnetron sputtering deposition.
Among all of these composite separators, Al2O3/SiO2/PVDF showed several advantages including excellent
thermal stability (no dimensional shrinkage at temperature up to 130
°C and an onset degradation temperature of 445 °C) and superb
electrolyte compatibility (340% electrolyte uptake). In addition,
the β phase of the fibrous PVDF membrane as well as the presence
of polar ceramic nanoparticles on the fiber surface can synergistically
improve the ion conductivity to 2.055 mS/cm at room temperature, which
is more than 8 times higher than that of the commercial polyethylene
(PE) separator. Performance of these ceramic nanoparticle-coated separators
in a lithium-ion battery demonstrated an improved discharge capacity
of 161.5 mAh/g and more than 84.3% capacity retention rate after 100
cycles. The ceramic nanoparticle-coated PVDF separators also maintained
58.4% capacity at a high current density of 8C, which is better than
the 49.8% capacity for the commercial PE separator. Therefore, the
ceramic nanoparticle-coated PVDF membrane proves to be a promising
separator for a high-power and more secure lithium-ion battery.
Abstract-This paper reports the first quantitative comparison study of elastic and viscoelastic properties of oocytes from young and aged mice. A force measurement technique, including a poly(dimethylsiloxane) (PDMS) cell holding device and a sub-pixel computer vision tracking algorithm, is utilized for measuring forces applied to an oocyte and resultant cell deformations in real time during oocyte manipulation. To characterize elastic and viscoelastic properties of the oocytes, a stress-relaxation indentation test is performed. A two-step, large-deformation mechanical model is developed to extract the mechanical properties of the oocytes from the measured force-deformation data. The experimental results demonstrate that the aged oocytes are significantly softer (instantaneous modulus: 2.2 vs. 5.2 kPa in young oocytes) but more viscous (relaxation time: 4.1 vs. 2.3 s in young oocytes) than the young oocytes.
An elastic spherical shell is compressed between two parallel rigid plates and undergoes large geometrical deformation. The convex surface conforms and adheres to the plates. The shell profile and contact stresses under large deformation are obtained numerically using a finite difference method. A thermodynamic energy balance following the classical Johnson-Kendall-Roberts (JKR) model is established to construct the adhesion mechanics, such that the sum of potential energy of the external load, elastic energy stored in the elastic shell, and surface energy to create new surface is minimized. Interrelationship between applied load, approach distance, contact radius, and deformed profile, as well as the ''pull-off'' phenomenon, are derived. A comparison is made between this model and existing models for a solid sphere in the literature.
NOMENCLATURE/ 0 angle between axis the outer normal of shell element and axis of symmetry of undeformed shell / angle between axis normal and axis of symmetry of deformed shell b rotation of normal r 0 distance from axis of symmetry before deformation R radius of undeformed shell
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.