•Dry coating of electrode particle with solid electrolyte for all-solid-state battery•Mechanism of dry coating process was revealed through parametric studies.•Electrode particles are coated by continuous layer of solid electrolyte.•No damage of electrode particles due to dry coatingWe have reported that a dry coating is a very promising process to produce a suitable composite particle for all-solid-state lithium-ion secondary batteries. We here present a parametric study of this dry coating process for further optimization and improvement. In the dry coating process, electrode particles were coated with solid electrolyte (SE) particles. LiNi1/3Co1/3Mn1/3O2 (NCM) was used as a host particle, while sodium sulfate (Na2SO4) was selected as a model material of sulfide SEs and used as a guest particle. A dry impact-blending process known as “Hybridizer” was used. Effects of critical process parameters including tip speed of rotor, processing time, and initial weight fraction of host and guest particles were investigated. Under insufficient impact force NCM particles were not fully covered with Na2SO4 particles, while under a sufficient impact force the discrete coating of Na2SO4 particles on the surface of NCM particles were observed. With an increase in the mechanical input energy per unit mass of Na2SO4, plastic deformation and coalescence of Na2SO4 particles were promoted, resulting in the continuous coating. With further increase in the mechanical input energy, breakage of the NCM particles was caused. The continuous coating exhibited a great advantage over the discrete coating for formation of the solid-solid interfacial contacts between NCM and Na2SO4 in the compressed pellet. Finally, the optimal processing conditions, where NCM particles are able to be coated by the continuous layer of much less amount of Na2SO4 (= 10 wt%) without breakage of NCM particles, were determined.

•The adhesion of colliding particles through multiple droplets was simulated.•Effect of droplet size on a particle-particle adhesion was analyzed.•Critical velocity for particle adhesion increased with a decrease in droplet size.•Dissipation energy of particle motion was correlated with the critical velocity.In a fluidized bed spray granulation, a particle-particle adhesion by a liquid bridge, which shows dynamic motion due to moving particles, is the most fundamental phenomenon. Therefore, understanding of the particle-particle adhesion by such a dynamic liquid bridge is very important to elucidate mechanisms of particle agglomeration phenomenon in the wet granulation. In this study, the particle-particle adhesion phenomenon at the individual particle scale was analyzed using a direct numerical simulation. Collision of two particles mediated by binder droplets on a particle surface was simulated. In particular, the effect of droplet size under constant total liquid volume on adhesiveness of two colliding particles was investigated. In the present simulation, multiple liquid bridges were simultaneously formed, and these liquid bridges coalesced into single liquid bridge. The simulation results exhibited that the adhesiveness of particles increased with a decrease in the droplet diameter under a constant total liquid volume. In an initial stage of the particle growth in a fluidized bed spray granulation, the tendency of the calculations was consistent with experimental results. We revealed that the capillary pressure force and shapes of the liquid bridge are key factors for particle-particle adhesion at different droplet sizes under constant total liquid volume.Download high-res image (86KB)Download full-size image

Nanoparticles (NPs) have been attracting much attention for biomedical and pharmaceutical applications. In most of the applications, NPs are required to translocate across the cell membrane and to reach the cell cytosol. Experimental studies have reported that by applying an electric field NPs can directly permeate across the cell membrane without the confinement of NPs by endocytic vesicles. However, damage to the cell can often be a concern. Understanding of the mechanism underlying the direct permeation of NPs under an external electric field can greatly contribute to the realization of a technology for the direct delivery of NPs. Here we investigated the permeation of a cationic gold NP across a phospholipid bilayer under an external electric field using a coarse-grained molecular dynamics simulation. When an external electric field that is equal to the membrane breakdown intensity was applied, a typical NP delivery by electroporation was shown: the cationic gold NP directly permeated across a lipid bilayer without membrane wrapping of the NP, while a persistent transmembrane pore was formed. However, when a specific range of the electric field that is lower than the membrane breakdown intensity was applied, a unique permeation pathway was exhibited: the generated transmembrane pore immediately resealed after the direct permeation of NP. Furthermore, we found that the affinity of the NP for the membrane surface is a key for the self-resealing of the pore. Our finding suggests that by applying an electric field in a suitable range NPs can be directly delivered into the cell with less cellular damage.

•The adhesion of colliding particles through a droplet was simulated.•Effect of particle wettability on a particle-particle adhesion was analyzed.•Critical velocity for particle adhesion non-linearly changed with the wettability.In wet granulation processes, a liquid bridge formed between particles is not static but dynamic due to continuous motion of the particles. Therefore, understanding of the particle-particle adhesion by a dynamic liquid bridge is an important issue. We here conducted a direct numerical simulation of the particle-particle adhesion by a dynamic liquid bridge. The particle-particle adhesion of two colliding particles through a droplet on a particle surface was simulated. In particular, effect of particle wettability on a critical velocity for the particle adhesion (i.e., adhesiveness of the two colliding particles) was investigated. It was found that the critical velocity for the particle adhesion non-monotonically changed with the particle wettability. The critical velocity exhibited a local maximum with an increase in the contact angle, while the static liquid bridge force monotonically decreases with an increase in the contact angle. We revealed that a combined effect of the liquid bridge deformation and instantaneous liquid bridge force results in the non-monotonic dependence on the particle wettability.

For developing a scale-up method based on the kinematic and dynamic similarities of particle behavior, motion of particles in a commercial high shear mixer-granulator with different vessel sizes (2 to 112 L) were simulated using a three-dimensional discrete element method (DEM). Effects of the vessel size on the internal particle flow and the particle collision energy were analyzed. It was found that under the constant impeller tip speed magnitude of the internal particle shear flow can be nearly maintained at different vessel sizes. This implies that the constant impeller tip speed should be employed to achieve the kinematic similarity when scaling-up the high shear mixer-granulator. However, under the constant impeller tip speed the cumulative particle collision energy per unit time significantly decreased with an increase in the vessel size. This suggests that in order to achieve the dynamic similarity the granulation time should be adjusted so that the cumulative particle collision energy over the granulation time can be maintained at different vessel sizes. Based on the simulation results, we proposed a scale-up method in which the optimal granulation time can be determined to achieve the same cumulative particle collision energy at different vessel sizes while maintaining the same impeller tip speed. This method can provide both the kinematic and dynamic similarities between different vessel sizes. Validity of the proposed scale-up method was confirmed by an experiment of wet-granulation using a commercial high shear mixer-granulator with different vessel sizes (2 to 216 L).Effects of the vessel size on the particle motion in a high-shear mixer granulator were analyzed using a DEM. Based on the simulation results, two constant rules for the successful scale-up were proposed: i.e., the constant impeller tip speed and the constant cumulative particle collision energy. The experimental results well supported validity of the proposed scale-up method.Highlights► DEM simulation of particle motion in a high shear mixer-granulator was conducted. ► Effects of the vessel size on the particle flow and collision energy were analyzed. ► The kinematic similarity can be maintained under the constant impeller tip speed. ► The dynamic similarity can be maintained by adjusting the granulation time. ► The experimental results supported validity of the proposed scale-up method.