Molecular Dynamics Study of the Separation Behavior at the Interface between PVDF Binder and Copper Current Collector

In Li-ion batteries, the mechanical strengths at the interfaces of binder/particle and binder/current collector play an important role in maintaining the mechanical integrity of the composite electrode. In this work, the separation behaviors between polyvinylidene fluoride (PVDF) binders and copper current collectors are studied in the opening and sliding modes using molecular dynamics (MD) simulations. The simulation shows that the separation occurs inside the PVDF rather than at the interface due to the strong adhesion between PVDF and copper. This fracture behavior is different from the behavior of the PVDF/graphite basal plane that shows a clear separation at the interface. The results suggest that the adhesion strength of the PVDF/copper is stronger than that of the PVDF/graphite basal plane. The methodology used in MD simulation can directly evaluate the adhesion strength at the interfaces of various materials between binders, substrates, and particles at the atomic scales. The proposed method can therefore provide a guideline for the design of the electrode in order to enhance the mechanical integrity for better battery performance.

Thermal Desorption in Pure Hexane and Hexane/Butane Mixtures on Graphite

The results of an extensive study of desorption in hexane (monolayer and submonolayer) and hexane/butane mixtures initially adsorbed onto the graphite basal plane is presented. Molecular dynamics (MD) simulations are utilized to carry out atomistic simulations at temperatures 300≤T≤700 for all three cases studied. Results from submonolayer and monolayer hexane indicate that the desorption energy needed for the system to proceed with the desorption process is independent of the system’s coverage, which is in good agreement with experimental results. It is also found that simulations of desorption of hexane/butane mixtures yield a high ratio of butane molecules being desorbed from the surface at lower temperatures (300 K), suggesting a strong dependence of the desorption barrier upon alkane chain length. The results are discussed and compared to previous experimental and theoretical results.

Synthesis, Characterization and Application of Thin Film Carbon Nanotube Material

The non-catalytical chemical vapor deposition (CVD) method was used to grow carbon thin film material consisting of plate-like nanosized graphite crystallites and multiwall carbon nanotubes with predominant orientation of both species by their crystallographic plane, corresponding to a graphite basal plane, along a normal to the film surface. A number of experimental techniques was used for examination and characterization of the film phase composition, morphology, and electron properties peculiarities. Low-field electron emission with highly density of emission sites and emission current was obtained for the film material and allow to demonstrate their applicability for sealed prototypes of light-emitting devices.