Design and Optimization of Composite Cathodes for Solid-State Batteries Using Hybrid Carbon Networks with Facile Electronic and Ionic Percolation Pathways.

Solid-state batteries (SSBs) have emerged as a promising alternative to conventional liquid electrolyte batteries due to their potential for higher energy density and improved safety. However, achieving high performance in SSBs is difficult because of inadequate contact and interfacial reactions that generate high interfacial resistance, as well as inadequate solid-solid contact between electrodes. These chronic issues are associated with inhomogeneous ion and electron transport networks owing to imperfect solid-solid interfacial contact. This study developed an optimal interfacial engineering strategy to facilitate an ion-electron transport network by designing an active material (NCM622) uniformly filled with a thin layer of a solid electrolyte (garnet-type Li6.25Ga0.25La3Zr2O12) and conductive additives. The optimal composite electrode architecture enhanced the high capacity, high rate capability, and long-term cycle stability, even at room temperature, owing to the percolating network for facile ionic conduction that assured a homogeneous reaction. In addition to mitigating the mechanical degradation of the cathode electrode, it also reduced the crosstalk effects on the anode-solid electrolyte interface. Effectively optimizing the selection and use of conductive additives in composite electrodes offers a promising approach to addressing key performance-limiting factors in SSBs, including interfacial resistance and solid-solid contact issues. This study underscores the critical importance of cathode architecture design for achieving high-performance SSBs by ensuring that the interfaces are intact with solid electrolytes at both the cathode and anode interfaces while promoting uniform reactions. This study provides valuable insights into the development of SSBs with improved performance, which could have significant implications for a wide range of applications.

Heat-Induced Agglomeration of Amorphous Silicon Nanoparticles Toward the Formation of Silicon Thin Film.

The thermal behavior of silicon nanoparticles (Si NPs) was investigated for the preparation of silicon thin film using a solution process. TEM analysis of Si NPs, synthesized by inductively coupled plasma, revealed that the micro-structure of the Si NPs was amorphous and that the Si NPs had melted and merged at a comparatively low temperature (~750 °C) considering bulk melting temperature of silicon (1414 °C). A silicon ink solution was prepared by dispersing amorphous Si NPs in propylene glycol (PG). It was then coated onto a silicon wafer and a quartz plate to form a thin film. These films were annealed in a vacuum or in an N2 environment to increase their film density. N2 annealing at 800 °C and 1000 °C induced the crystallization of the amorphous thin film. An elemental analysis by the SIMS depth profile showed that N2annealing at 1000 °C for 180 min drastically reduced the concentrations of carbon and oxygen inside the silicon thin film. These results indicate that silicon ink prepared using amorphous Si NPs in PG can serve as a proper means of preparing silicon thin film via solution process.

Role of Drosophila EDEMs in the degradation of the alpha-1-antitrypsin Z variant.

The synthesis of proteins in the endoplasmic reticulum (ER) that exceeds the protein folding capacity of this organelle is a frequent cause of cellular dysfunction and disease. An example of such a disease is alpha-1-antitrypsin (A1AT) deficiency, caused by destabilizing mutations in this glycoprotein. It is considered that the mutant proteins are recognized in the ER by lectins and are subsequently degraded through the proteasome, leading to a deficiency in this enzyme in the afflicted patients. We previously established a Drosophila model of this disease by overexpressing the null Hong Kong (NHK) allele of this gene and found that the Drosophila lectin, ER degradation-enhancing α-mannosidase-like protein 2 (EDEM2), can accelerate the degradation of A1AT when overexpressed. NHK is a rare allele, and in this study, we investigated in depth the mechanisms through which Drosophila EDEMs affect the degradation of the Z variant, which is the predominant disease allele. Specifically, we report that the Z allele does not activate ER stress signaling as prominently as the NHK allele, but similarly requires both Drosophila EDEM1 and EDEM2 for the degradation of the protein. We demonstrate that EDEMs are required for their ubiquitination, and without EDEMs, glycosylated A1AT mutants accumulate in cells. These results support the role of the EDEM-mediated ubiquitination of the alpha-1-antitrypsin Z (ATZ) allele, and establish a Drosophila model for the study of this protein and disease.

A Modified Oxidative Refinement Process for Removing Boron from Molten Silicon Under Enhanced Electromagnetic Force.

The removal of boron is one of the main challenges in the purification of metallurgical grade silicon destined for low-cost photovoltaic applications. However, boron is very difficult to remove in its elemental form due to its large segregation coefficient in silicon and its low vapor pressure. The removal of boron by slag treatment is today regarded as a highly promising method, but its refining efficiency is relatively low. Also, the reduction of boron by plasma treatment exhibits a high refining efficiency, but the processing cost is high due to the large amount of electricity consumed by the process. In this regard, the use of an oxidizing reactive gas in the refinement process offers some advantages both in terms of low energy consumption and promising refinement rates. Boron can be extracted in various gaseous forms as B(x)O(y) and/or B(x)H(z)O(y) phases, but the vapor pressure of B(x)H(z)O(y) is much greater than that of the other specie at a temperature of 1700 K. The present study reports a modified oxidative refining method designed to enhance the vaporization of boron as B(x)H(z)O(y) by blowing gaseous water onto the silicon melt in a segmented crucible to enhance the electromagnetic force, whereby the processing cost can be dramatically reduced due to the use of a reusable quartz crucible in a graphite crucible. An initial boron content of 13 ppm in the metallurgical grade silicon was significantly decreased to 0.3 ppm by the employment of 1.7SLM Ar + 100 ml/h H2O. Also, a mechanism capable of reducing boron based on thermodynamic considerations is proposed.

Numerical simulation of solid liquid interface behavior during continuous strip casting process.

A new metal-strip-casting process called continuous strip-casting (CSC) has been developed for making thin metal strips. A numerical simulation model to help understand solid-liquid interface behavior during CSC has been developed and used to identify the solidification morphologies of the strips and to determine the optimum processing conditions. In this study, we used a modified level contour reconstruction method (LCRM) and the sharp interface method to modify interface tracking, and performed a simulation analysis of the CSC process. The effects of process parameters such as heat-transfer coefficient and extrusion velocity on the behavior of the solid-liquid interface were estimated and used to improve the apparatus. A Sn (Tin) plate of dimensions 200 x 50 x 1 mm3 was successfully produced by CSC for a heat-transfer coefficient of 104 W/m2 K and an extrusion velocity of 0.2 m/s.

Numerical simulation and fabrication of silicon sheet via spin casting.

A spin-casting process for fabricating polycrystalline silicon sheets for use as solar cell wafers is proposed, and the parameters that control the sheet thickness are investigated. A numerical study of the fluidity of molten silicon indicates that the formation of thin silicon sheets without a mold and via spin casting is feasible. The faster the rotation speed of graphite mold, the thinner the thickness of sheet. After the spread of the molten silicon to cover the graphite mold with rotation speed of above 500 rpm, the solidification has to start. Silicon sheets can be produced by using the centrifugal force under appropriate experimental conditions. The spin-cast sheet had a vertical columnar microstructure due to the normal heat extraction to the substrate, and the sheet lifetime varied from 0.1 microS to 0.3 microS measured by using the microwave photoconductance decay (MW-PCD) to confirm that the spin-cast silicon sheet is applicable to photovoltaics.

Study of the microstructures and lifetime of spin-cast silicon sheets for photovoltaics.

Silicon sheets were fabricated by a new fabricating method, spin casting with various rotation speeds of the graphite mold. The microstructure of spin-cast silicon sheets were investigated using an electron probe microanalyzer (EPMA) and scanning electron microscope/electron backscatter diffraction/orientation image micrograph, and the lifetime of the sheets was mapped using microwave photoconductance decay. The silicon sheets were vertically aligned, with sizes ranging from tens of microns to one hundred microns. The as-grown lifetime was measured and found to range from 0.049 micros to 0.250 micros. The ASTM number was plotted against the lifetime using ASTM E112 to estimate the grain size. Approximately half of the grain boundaries seemed electrically inactive with meaning of no recombination center since the grains were growth directionally, especially in a longitudinal aligned. It was confirmed that the lifetime of spin-cast sheets makes them suitably applicable for photovoltaics compared to those produced by alternative ribbon-producing methods.

SiO(x) nanoparticles synthesized by an evaporation and condensation process using induction melting of silicon and gas injection.

SiO(x) nanoparticles were synthesized using a specially designed induction melting system equipped with a segmented graphite crucible. The graphite crucible with the segmented wall was the key to enhancing the evaporation rate due to the increase of the evaporation area and convection of the silicon melt. Injection of the gas mixture of oxygen (O2) and argon (Ar) on silicon (Si) melt caused the formation of SiO(x) nanoparticles. The evaporated SiO(x) nanoparticles were then cooled and condensed in a process chamber. The effects of the O2/Ar ratio in the injection gas on the microstructures of the SiO(x) nanoparticles were then investigated. Synthesized SiO(x) nanoparticles were proven to be of a homogeneous amorphous phase with average diameters of 30-35 nm. The microstructures were independent from the O2/Ar ratio of the injected gas. However, x increased from 1.36 to 1.84 as the O2/Ar ratio increased. The purity of the synthesized nanoparticles was about 99.9%. SiO(x) nanoparticles could be applied as the active anode material in a lithium (Li) ion secondary battery.

Formation of silicon sheet on a rotating substrate.

A spin casting process to fabricate polycrystalline silicon sheets for use as solar cell wafers is presented and the parameters that control the sheet thickness are investigated. The computational model for the spin casting is proposed in order to understand the melt flow and solidification behaviors in the mold. The effect of the rotating speed of the mold and substrate morphology on the silicon sheets is studied via computer simulations, and the simulation results are compared with the experimental results. The numerical study of the fluidity and solidification behavior of the silicon predicted that the formation of rectangular sheets via spin casting is feasible, and the subsequent experiment confirmed this prediction. Using a square mold, rectangular silicon sheets can be produced under appropriate experimental conditions. Microstructural analyses verified the presence of long columnar structures on the sheets.

Effects of process conditions on the properties of silicon nanoparticles synthesized by gas phase reactions using inductive coupled plasma.

Silicon nanoparticles were synthesized by passing monosilane through a quartz tube wrapped with Inductive Coupled Plasma (ICP) coil. Microstructures of synthesized silicon nanoparticles were investigated with various process conditions. To research the effects of process parameters on the properties of nanoparticles, we verified the partial pressure of monosilane, the plasma power and the working pressure. The highly crystalline silicon nanoparticles were only achieved at the proper partial pressure of the reactive gas and plasma power. Partial pressure determined not only the particle size but also the crystallinity of the nanoparticles. The plasma power was controlled from 50 to 100 W which determined not the particle size but the crystallinity of nanoparticles. Especially, too low a power resulted in amorphous particles with an average sizes of 5.25 nm. As the working pressure increased, the amount of produced nanoparticles linearly increased and the maximum production yield was at 76 mg/hr. Controlling those parameters, we achieved monodispersed single crystalline silicon nanoparticles with an average diameter of 7.52 nm. Silicon nanoparticles in this study can be applied to light absorbing material for solar cells and the wavelength down-converter material of Light Emitting Diode (LED).

Effects of annealing conditions on microstructures of thin film using crystalline silicon nanoparticles for printable electronics.

Silicon thin film was formed by dropping silicon ink on a single-crystalline silicon substrate and further annealing. The effects of the annealing conditions on the microstructures of thin film were investigated in order to obtain a crystalline silicon thin film for application in the field of printable electronics. Silicon ink was prepared by dispersing silicon nanoparticles synthesized using inductive coupled plasma in a solvent, namely, propylene glycol. The silicon nanoparticles in the as-synthesized film were observed to melt at a temperature of less than 1000 degrees C, and a highly crystalline silicon thin film was obtained by annealing at 800 degrees C for 180 min.