Influence of cathode calendering density on the cycling stability of Li-Ion batteries using NMC811 single or poly crystalline particles

Calendering of battery electrodes is a commonly used manufacturing process that enhances electrode packing density and therefore improves the volumetric energy density. While calendering is standard industrial practice, it is known to crack cathode particles, thereby increasing the electrode surface area. The latter is particularly problematic for new Ni-rich layered transition metal oxide cathodes, such as NMC811, which are known to have substantial surface-driven degradation processes. To establish appropriate calendering practices for these new cathode materials, we conducted a comparative analysis of uncalendered electrodes with electrodes that have a 35% porosity (industrial standard), and 25% porosity (highly calendered) for both single crystal (SC) and polycrystalline (PC) NMC811. PC cathodes show clear signs of cracking and decrease in rate capability when calendered to 25% porosity, whereas SC NMC811 cathodes, achieve better cycling stability and no penalty in rate performance at these high packing densities. These findings suggest that SC NMC811 cathodes should be calendered more densely, and we provide a comprehensive overview of both electrochemical and material characterisation methods that corroborate why PC and SC electrodes show such different degradation behaviour. Overall, this work is important because it shows how new single-crystal cathode materials can offer additional advantages both in terms of rate performance and cycling stability by calendaring them more densely

Data set for Nylon-6 based nanocomposite films for capacitor applications

High quality images and graphs used for publication of the article "Nylon-6 based nanocomposite films for capacitor applications" are in the sheets from 'Fig 1' to 'Fig 3' of this excel file. The data used to plot the graphs in the article are in the sheet 'All graphs data'

Nylon-6 based nanocomposite films for capacitor applications

Nylon-6 and Al based nanocomposite films were fabricated via a scalable vacuum co-deposition technique. The relative deposition rates of the constituent phases - nylon-6 (matrix) and Al (filler) - were varied systematically to yield films of different compositions and their dielectric properties, particularly the measured dielectric constants k, were compared with predictions of effective medium expressions. The effect of absorbed water, temperature and heat treatment on k of the nano-films were studied. X-ray photoelectron spectroscopy revealed the presence of an Al-based oxide, which was correlated to the observed enhancement in the dielectric properties of the nanocomposites. The effect of the relative deposition rates of the constituent phases on k and the chemistry of the deposited films fabricated via co-deposition was studied and explained using X-ray photoelectron spectroscopy results

Core-shell nanoparticles and enhanced polarization in polymer based nanocomposite dielectrics.

We present a detailed study of the evolution and nature of metallic core-oxide shell particles and the role of nanostructure in the physics of enhanced polarization in polymer-nanocomposite (PNC) based dielectrics. Nylon-6 based PNCs consisting of aluminium (core)-aluminium oxide (shell) nanoparticles were fabricated by a vacuum deposition technique. Their resulting high polarizability was closely related to the formation and chemistry of the core-shell structure that was revealed by transmission electron microscopy to comprise a highly-defective, strained and non-stoichiometric semi-crystalline/amorphous Al-oxide shell

Electron microscopy of multi-layered polymer-nanocomposite based dielectrics

Vacuum deposited polymer-nanocomposites (PNCs) comprising alternate layers of metal (Al/Ag) (filler) and polymer (nylon-6) (matrix) have been investigated using chemical, impedance spectroscopy and microstructural characterisation techniques. Electron microscopy investigations revealed the morphology, nanostructure and phases of nano-scale core (metal)-shell (oxide) particles and metallic nano-islands in Al and Ag based PNCs respectively. Evaporation of Al yielded islands of angular core-shell nanoparticles in an Al-oxide/nylon-6 matrix whereas Ag yielded rounded, discrete nanoparticles in nylon-6 matrix. The high particle surface area and an affinity for oxygen formed oxide shells in Al nanoparticles and was critical to charge accumulation and enhanced dielectric behaviour; in contrast, Ag showed little oxidation and less charge accumulation. With an increase in the thickness of the deposited metal layer, Al formed a continuous film of particles whereas Ag condensed to form interconnected nano-islands. This microstructural study is useful in conceptualising better dielectrics based on PNCs. © Published under licence by IOP Publishing Ltd

Fabrication of nanoscale features on ultra-thin glass-based dielectrics via self-masking and preferential etching to enhance capacitance

Flexible capacitors based on ultra-thin glass (30 μm thick) were fabricated and the effect of nanoscale surface modification on the dielectric properties was studied. The ultrathin glass samples were partially masked by the deposition and self-organisation of Ag-islands and then preferentially etched to produce a controlled topography. The etching duration was varied and its effect on Ag content and dielectric properties were studied by employing atomic force microscopy (AFM), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), and impedance spectroscopy. The AFM studies revealed the presence of nanoscale ‘peaks’, which were distributed across the surface of the glass, that following etching showed enhanced capacitance. Surface modification of glass using self-organised nano-scale metal island masks is shown to be an effective route to enhance the use of ultra-thin glass in capacitor applications

Engineering the nanostructure of a polymer-nanocomposite film containing Ti-based core-shell particles to enhance dielectric response.

Nylon-6 based polymer-nanocomposite (PNC) dielectrics containing nano-regions of Ti-only and Ag + Ti have been manufactured by layer-by-layer deposition. By varying the thickness and deposition rate of individual layers, the PNC structure was manipulated at the nano-scale and then studied using various types of transmission electron microscopy (TEM). Enhanced PNC dielectric properties, with a dielectric constant k as high as ∼73, were shown to relate critically to in situ reactions and the detailed nano-arrangement of the resulting Ti (core)-TiOx (shell) and Ag nanoparticles

Fabrication of nanoscale features on ultra-thin glass-based dielectrics via self-masking and preferential etching to enhance capacitance

Flexible capacitors based on ultra-thin glass (30 μm thick) were fabricated and the effect of nanoscale surface modification on the dielectric properties was studied. The ultrathin glass samples were partially masked by the deposition and self-organisation of Ag-islands and then preferentially etched to produce a controlled topography. The etching duration was varied and its effect on Ag content and dielectric properties were studied by employing atomic force microscopy (AFM), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), and impedance spectroscopy. The AFM studies revealed the presence of nanoscale ‘peaks’, which were distributed across the surface of the glass, that following etching showed enhanced capacitance. Surface modification of glass using self-organised nano-scale metal island masks is shown to be an effective route to enhance the use of ultra-thin glass in capacitor applications

Nylon-6 based nanocomposite films for capacitor applications

Nylon-6 and Al based nanocomposite films were fabricated via a scalable vacuum co-deposition technique. The relative deposition rates of the constituent phases - nylon-6 (matrix) and Al (filler) - were varied systematically to yield films of different compositions and their dielectric properties, particularly the measured dielectric constants k, were compared with predictions of effective medium expressions. The effect of absorbed water, temperature and heat treatment on k of the nano-films were studied. X-ray photoelectron spectroscopy revealed the presence of an Al-based oxide, which was correlated to the observed enhancement in the dielectric properties of the nanocomposites. The effect of the relative deposition rates of the constituent phases on k and the chemistry of the deposited films fabricated via co-deposition was studied and explained using X-ray photoelectron spectroscopy results

Core-shell nanoparticles and enhanced polarization in polymer based nanocomposite dielectrics.

We present a detailed study of the evolution and nature of metallic core-oxide shell particles and the role of nanostructure in the physics of enhanced polarization in polymer-nanocomposite (PNC) based dielectrics. Nylon-6 based PNCs consisting of aluminium (core)-aluminium oxide (shell) nanoparticles were fabricated by a vacuum deposition technique. Their resulting high polarizability was closely related to the formation and chemistry of the core-shell structure that was revealed by transmission electron microscopy to comprise a highly-defective, strained and non-stoichiometric semi-crystalline/amorphous Al-oxide shell