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Solid-state lithium batteries have become an attractive alternative to traditional lithium-ion batteries due to their enhanced safety and energy density potential. However, their current level is still immature from a cell engineering perspective. This work presents ultimate design principles for achieving high energy density in practical solid-state lithium batteries. Our proposed design logic is based on evaluating the microstructural and architectural parameters that significantly impact energy density. We demonstrate the feasibility of this principle through the fabrication of a 10-layer stacked solid-state pouch cell with a solid polymer electrolyte, resulting in an energy density of 280 Wh kg−1 and 600 Wh L−1. This research provides a promising path forward for the scientific community to pursue practical, high-energy-density solid-state batteries that can meet the growing demand for energy storage solutions.

Nanoparticles having four different ratios of crystalline silicon (Si) cores and amorphous SiOx shells were synthesized by using a microwave-generated plasma. Their microstructures were analyzed to find quantitative relationships with electrochemical properties. By measuring XRD, SEM, HR-TEM, and Raman spectra of four samples with different core-shell microstructures, the quantitative fractions of crystalline Si core and amorphous SiOx shell in the nanoparticles were calculated. Also, electrochemical properties of the nanoparticles were measured and compared with the calculated fractions. The electrochemical properties such as the initial reversible capacity, the initial coulombic efficiency, and the capacity retention exhibited tendencies remarkably similar to those implied by the calculated fractions. Analysis of each sample's dQ/dV profile also gave us good evidence of understandable relationships between the fractions and electrochemical properties. Details of calculating the fractions from microstructural data are given, with suitable consideration having been given to the fact that several assumptions could lead to errors during the analysis. The approach introduced in this research offers a good means of analysis with which to further the optimal design of nanoparticle microstructure for Li-ion battery anodes.

Effects of SiOx or C shells on electrochemical properties of Si nanoparticles were investigated. SiOx shells with thickness of 10~15 nm were formed on homogeneously crystalline Si nanoparticles. Incase of Si-C nanoparticles, there were 30~40 layers of C with a number of defects. Li-ion batteries were fabricated with the above-mentioned nanoparticles, and their electrochemical properties were measured. Pristine Si shows a high IRC (initial reversible capacity) of 2,517 mAh/g and ICE (initial columbic efficiency) of 87%, but low capacity retention of 22%, respectively. SiOx shells decreased IRC (1,534 mAh/g) and ICE (54%), while the retention increased up to 65%, which can be explained by irreversible phases such as LiO2 and Li2SiO3. C shells exhibited no differences in IRC and ICE compared to the pristine Si but an enhanced retention of 54%, which might be from proper defect structures.

In this study, 1.0 mol% CuO-added (NaxK1−x)NbO3 (CNxK1−xN) ceramics with 0.0 ≤ x ≤ 0.5 were sintered at a relatively low temperature of 960°C. A large Qm value (≥1750) was obtained for the specimens with x ≤ 0.2 owing to the hardening effect of Cu2+ ions, indicating that a large number of Cu2+ ions had replaced Nb5+ ions in these ceramics. The double polarization versus electric field (P–E) hysteresis loop was observed for the specimens with x ≤ 0.2, and was explained by the defect polarization (Pd) formed between Cu2+ ions and O2− vacancies. These specimens also exhibited a sprout-shaped strain versus electric field (S–E) curves with a large strain of 0.14%–0.15% at 8.0 kV/mm because of the internal bias field produced by Pd. For the CN0.2K0.8N ceramic, a double P–E hysteresis loop was maintained at 125°C without remnant polarization. Moreover, this ceramic showed a large strain of 0.175% after 104 cycles when a high electric field of 8.0 kV/mm was continuously applied to the specimens during each cycles. Therefore, CN0.2K0.8N is a useful lead-free piezoelectric ceramic for multilayer actuators.

Silicon-carbon (Si-C) composites with various weight ratios were prepared through heat treatment of water-soluble carboxymethyl cellulose (CMC) with Si nanoparticles synthesized by using an inductively-coupled plasma. Microstructures of the Si-C composites were thoroughly investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. The results indicate that we obtained a micro-sized Si-C composite with homogeneously-distributed crystalline Si nanoparticles in an amorphous C-matrix. Pores, which were due to the volatilization of CO2 from CMC during heat treatment, was detected when the concentration of carbon was increased. The electrochemical properties of those Si-C composites for use as anode materials in lithium-ion batteries (LIBs) were also investigated. The C-matrix enhanced the capacity retention, as well as the rate capability of Si nanoparticles, due to the dense and homogeneous microstructures of the composite. The Si-C composites (7:3 weight ratio) retained a reversible capacity of > 1,000 mAh/g with a capacity retention of 88.9% even after 100 cycles. The reversible capacity ratio at a 1.5 C-rate was about 80% as compared with that at a 0.1 C-rate.

A room temperature refining process using a new acidic mixture was investigated for the purification of metallurgical grade-silicon (MG-Si) with an average particle size of 617 μm. MG-Si typically contains precipitated metal impurities, such as iron (Fe), aluminum (Al) and titanium (Ti), in the triple points of grain boundaries. These metal impurities tend to concentrate within the laminar structure at grain boundaries during solidification due to their different segregation coefficients and are leached with acid at different rates because of their different reactivities with acid. The addition of acetic acid (CH3COOH) to a conventional acid mixture composed of nitric acid (HNO3) and hydrofluoric acid (HF) resulted in improved extraction of the main metal impurities. This new acid mixture efficiently extracted Al, which is known to be particularly difficult to remove with conventional acid leaching agents, such as hydrochloric acid (HCl), nitric acid (HNO3), and hydrofluoric acid (HF). The recorded decreases of the Fe and Al concentrations in the material followed two distinct leaching events. The first decrease was due to the extraction of impurities located on the particle surface; the second occurred when the acid leaching time exceeded 15 h. This second leaching event may be due to the removal of metal impurities located deep in the material's pores and deep within the bulk structure of the MG-Si particles. After 25 h of leaching MG-Si with an acid mixture composed of HNO3, HF, and CH3COOH, the purity of the material increased from 99.74 to 99.99% with extraction efficiencies of 99.92 for Fe and 99.98% for Al and Ti.

A silicon substrate with the dimensions of 100 × 140 × 0.3 mm was grown directly from liquid silicon with gas pressure. The silicon melt in the sealed melting part was injected into the growth part at applied pressure of 780–850 Torr. The solidified silicon substrate was then transferred by the pull of the cooled dummy bar. A desirable structure with a liquid-solid interface perpendicular to the pulling direction was formed when the mold temperature in the solidification zone of the growth part was much higher than that of the dummy bar, as this technique should be able to overcome thermal loss through the molds and the limited heat flux derived from the very narrow contact area between the silicon melt and the dummy bar. In addition, because the metallic impurities and expansion of volume during solidification are preferably moved to a liquid phase, a high-quality silicon substrate, without defects such as cracks and impurities in the substrate, could be manufactured in the interface structure. The present study reports the experimental findings on a new and direct growth system for obtaining silicon substrates characterized by high quality and productivity, as a candidate for alternate routes for the fabrication of silicon substrates.

The most desirable approach to the hydrometallurgical process consists in using larger silicon particles by exposing the metallic impurities contained in the silicon to its surface via a thermallyactivated elution prior to chemical treatment. The present study reports experimental findings concerning the effect of a thermal pre-treatment using a mixture of 5-wt% nitric acid and 2.5-wt% hydrofluoric acid for the purification of metallurgical-grade silicon particles of different sizes on the hydrometallurgical process. The extraction rates of metallic impurities from inside the silicon were in inverse proportion to the size of the silicon particle. However, the effect of the thermal pre-treatment on the extraction rate became greater with increasing particle size.

With direct growth technologies for obtaining ribbon-type silicon (Si) wafers from molten Si, the horizontal growth process is much faster than the vertical one in terms of the growth rate of the wafer. However, such a fast growth rate is likely to create grains of a relatively small size in the Si wafer, resulting in limited efficiency caused by grain boundary recombination. In this regard, controlling the grain growth behavior of the Si wafer with processing parameters such as the temperature of the substrate and its moving speed is very important in the horizontal growth process. The present investigation produced the experimental findings concerning the processing parameters for controlling the grain size. The size of the grains on the surface of the Si wafer increased to around 180 μm at a lower substrate temperature and a slower the moving speed of the substrate due to the increasing thickness of the Si wafer. However, the growth rate of the grains was observed to have little relation to the variations in the wafer thickness resulting from the processing parameters unless the nucleation behavior had been controlled.

A novel strategy for introducing ion-permselective properties in a conventional polyethylene (PE) separator to inhibit the shuttle effect of polysulfides in high-performance lithium–sulfur batteries is reported. This was accomplished by taking advantage of the pH-responsive multilayers of weak polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) assembled on the PE separator using layer-by-layer (LbL) assembly. It was found that the cationic permselectivity (permeability of cation/anion) of an ultrathin multilayer coated separator is highly tunable with respect to the number of bilayers and external pH, benefiting from fine tuning of the internal charge density of the multilayered films. The movement of polysulfide anions was significantly inhibited by five bilayers of PAH/PAA (ca. 98% with multilayers assembled at pH 3/3), while the movement of Li cations was preserved. As a result, the ion-permselective separator demonstrated a high initial reversible capacity of ca. 1418 mA h g−1 with multilayers assembled at pH 3/3 because of the good permselectivity and the enhanced wetting properties of the LbL treated separator for electrolytes, leading to a significantly improved Coulombic efficiency as compared to a conventional PE separator, i.e., almost 100% over 50 cycles. We anticipate that the permselectivity controllable coating method will be applied for various other membrane technologies.

The recovery of copper from spent photovoltaic ribbon was conducted using thermal treatment method at the range of temperature of to under inert atmosphere. The coating layer consisted of lead of 68.99 wt.% and tin of 31.21 wt.% was melted down at elevated temperatures and was collected on the bottom of crucible. The chemical composition of copper ribbon after thermal treatment was analyzed by ICP-MS (Inductively coupled plasma mass spectrometry) and the purity of copper was found to be obtained up to about 96 wt.% regardless of temperatures. The cross-sectional area of the specimen was also examined by SEM (scanning electron microscopy) and EDX (energy dispersive X-ray microscopy).

A ribbon-type polycrystalline silicon wafer was directly fabricated from liquid silicon via a novel technique for both a fast growth rate and large grain size by exploiting gas pressure. Effects of processing parameters such as moving speed of a dummy bar and the length of the solidification zone on continuous casting of the silicon wafer were investigated. Silicon melt extruded from the growth region in the case of a solidification zone with a length of 1cm due to incomplete solidification. In case of a solidification zone wieh a length of 2 cm, on the other hand, continuous casting of the wafer was impossible due to the volume expansion of silicon derived from the liquid-solid transformation in solidification zone. Consequently, the optimal length of the solidification zone was 1.5 cm for maintaining the position of the solid-liquid interface in the solidification zone. The silicon wafer could be continuously casted when the moving speed of the dummy bar was 6 cm/min, but liquid silicon extruded from the growth region without solidification when the moving speed of the dummy bar was 9 cm/min. This was due to a shift of the position of the solid-liquid interface from the solidification zone to the moving area. The present study reports experimental findings on a new direct growth system for obtaining silicon wafers with both high quality and productivity, as a candidate for an alternate route for the fabrication of ribbon-type silicon wafers.

Silicon (Si) wafer was grown by using direct growth from Si melt and contaminations of wafer during the process were inves-tigated. In our process, BN was coated inside of all graphite parts including crucible in system to prevent carbon contamination. Inaddition, coated BN layer enhance the wettability, which ensures the favorable shape of grown wafer by proper flow of Si melt incasting mold. As a result, polycrystalline silicon wafer with dimension of 156× 156 mm and thickness of 300 ± 20 um was suc-cessively obtained. There were, however, severe contaminations such as BN and SiC on surface of the as-grown wafer. While BNpowders were easily removed by brushing surface, SiC could not be eliminated. As a result of BN analysis, C source for SiC wasfrom binder contained in BN slurry. Therefore, to eliminate those C sources, additional flushing process was carried out before Siwas melted. By adding 3-times flushing processes, SiC was not detected on the surface of as-grown Si wafer. Polycrystalline Siwafer directly grown from Si melt in this study can be applied for the cost-effective Si solar cells.Key words: Silicon, Wafer, Direct growth, Contamination, Silicon carbide

SiO1.39 nanoparticles synthesized by using an evaporation and condensation process were composited with phenol resin and conducting carbon (C), and their microstructures and electrochemical properties were investigated. A dense, micro-sized SiO1.39-C composite was synthesized to prevent capacity fading of the SiO x nanoparticles. To densify and coarsen this composite, we carried out pelletizing, annealing and crushing of the sample. The electrical conductivity was also improved by the composition without any structural change. Crushed particles were used as an anode material for a Li-ion battery, and its cyclic performance was evaluated. By composition, the coulombic efficiency was observed to increase from 93.6 to 97.5% at the 5 th cycle, and it continued increasing with each additional cycle. For the composite annealed at 1,000 °C in a 4-vol.% H2/Ar atmosphere, the specific capacity and the coulombic efficiency at the 20 th cycle were measured as 426 mAhg−1 and 99.7%, respectively.

The high cost of crystalline silicon solar cells has been considered as one of the major obstacles to their terrestrial applications. Spin on doping (SOD) is presented as a useful process for the manufacturing of low cost solar cells. Phosphorus (P509) was used as an n-type emitters of solar cells. N-type emitters were formed on p-type EFG ribbon Si wafers by using a SOD at different spin speed (1,000~4,000 rpm), diffusion temperatures (), and diffusion time (5~30 min) in atmosphere. With optimum condition, we were able to achieve cell efficiency of 14.1%.

Ribbon silicon solar cells have been investigated because they can be produced with a lower material cost. However, it is very difficult to get good texturing with a conventional acid solution. To achieve high efficiency should be minimized for the reflectance properties. In this paper, acid vapor texturing and anti-reflection coating of SiNx was applied for EFG Ribbon Si Wafer. P-type ribbon silicon wafer had a thickness of 200 μm and a resistivity of 3 Ω-㎝. Ribbon silicon wafers were exposed in an acid vapor. Acid vapor texturing was made by reaction between the silicon and the mixed solution of HF : HNO3.. After acid vapor texturing process, nanostructure of less than size of 1 μm was formed and surface reflectance of 6.44% was achieved. Reflectance was decreased to 2.37% with anti-reflection coating of SiNx.

Silicon nanoparticles were synthesized using inductively coupled plasma (ICP), and their microstructures were investigated by using scanning electron microscopy, X-ray diraction, and transmission electron microscopy. Applying ICP in a tube reactor, the shape of the plasma region was very sensitive to the process conditions and reactor geometry. For the control of the plasma shapes, an additional inner tube was inserted into the quartz tube reactor. To evaluate the advantages of this double tube reactor, we investigated the microstructures of the silicon nanoparticles synthesized in this manner under various process conditions. This additional tube reduced the length of the plasma zone and formed highly-dense plasma only near the ICP coil. Injection of the reactive gas through the inner tube resulted in the formation of single-crystalline nannoparticles with 13.47 nm diameters.

Europium-activated calcium aluminium silicate phosphors were synthesized for the first time and the structures and luminescence characteristics of these phosphors were investigated. The phosphors in this study emitted blue, green, and even red light depending on the starting milterials and annealing conditions for synthesis. In addition, the structure was also changed when the different starting materials were used. When was used as a starting material, tetragonal was formed. However, pure green light was emitted when the annealing was conducted in reduced atmosphere and red one was emitted by annealing in air. In the case of as a starting material, triclinic was formed and only pure blue emission was observed. Moreover, this blue phosphor exhibited higher intensity than that of commercial YAG:Ce phosphor, which showed the possibility of application on the phosphor for new light source such as a UV-LED.

BaTi4O9 thin films were grown on a Pt/Ti/SiO2/Si substrate using rf magnetron sputtering and the structure of the thin films were then investigated. For the films grown at low temperature (≤350°C), an amorphous phase was formed during the deposition, which then changed to the BaTi5O11 phase when the annealing was conducted below 950°C. However, when the annealing temperature was higher than 950°C, a BaTi4O9 phase was formed. On the contrary, for the films grown at high temperature (>450°C), small BaTi4O9 grains were formed during the deposition, which grew during the annealing. The homogeneous BaTi4O9 thin films were successfully grown on Pt/Ti/SiO2/Si substrate when they were deposited at 550°C and subsequently rapid thermal annealed at 900°C for 3 min.

Si-SiOx nanoparticles with core-shell structure were synthesized by atmospheric microwave plasma using tetrachloride silicon. Crystalline Si core and amorphous SiOx shell could be controlled by various process conditions. In order to determine the Si-SiOx core-shell ratio for application to anode materials in lithium-ion battery, microstructures and electrochemical properties of synthesized Si-SiOx nanoparticles with various core-shell ratios were investigated. From a result of HR-TEM analysis, there are Si nanoparticles with thickness of 1~3 nm SiOx shell which are only native oxide layer on crystalline Si core. Typical electrochemical behaviour of Si such as high initial reversible capacity and poor retention was observed in those nanoparticles. The shell thickness of Si-SiOx nanoparticles affects the electrochemical properties such as first reversible capacity, retention. For example, nanoparticles with shell thickness of 10 nm exhibited the first reversible capacity of about 1,274 mAh/g and retention at 50th cycle of about 94.8 %. As a result, electrochemical properties could be controlled by the core-shell ratios of Si-SiOx nanoparticles.

SiOx nanoparticles were synthesized by using an evaporation and condensation process involving induction melting of silicon (Si) chunks followed by the injection of a H2/Ar mixed gas into the melt. In particular, this research studied the effects of hydrogen gas on the nanoparticles’ microstructural and electrochemical properties, etc. During the microstructural analysis, regardless of H2 content, all the nanoparticles were observed to have random shapes; their average particle sizes were 30 ∼ 35 nm. However, a crystalline Si phase, even though it was a small amount, was formed when H2/Ar gas was injected. From the X-ray photoelectron spectroscopy (XPS) analysis, the amount of the SiO2 phase in SiOx decreased when the H2/Ar gas ratio was higher than 1.0 vol.%. Injected hydrogen produced a Si-H network in SiOx, and the Si-H concentration was independent of the amount of injected gas. Consequently, due to hydrogen incorporation, not only was a crystalline Si phase formed, but also the amount of the SiO2 phase decreased. In addition, Si-H bonds were formed in the nanoparticles. The crystalline Si phase and the relatively small amount of the SiO2 phase resulted in an enhancement of the Li-ion capacity when those nanoparticles were applied as an anode material for a Li-ion battery. Furthermore, cycle performance was improved even when hydrogen was incorporated. For the sample synthesized with 5.0-vol.% H2/Ar gas, the discharge capacity and the columbic efficiency at the 21st cycle were 889.1 mAhg−1 and 95.0%, respectively.

A new photo-cross-linkable poly(acrylic acid) (PAA) polymer functionalized with a photoreactive benzophenone group (PAA-BP) was synthesized and examined as a binder for Si-based anodes. Upon UV irradiation, the PAA-BP binders formed an irreversible cross-linked structure through the formation of a new three-dimensional C–C bond network between the benzophenone moiety and the PAA backbone. The photo-cross-linked PAA-BP binder demonstrated a marginal volume expansion (38%) after full lithiation, compared to conventional binders and this resulted in an improved cycle performance of the Si anode over 100 cycles with a high reversible capacity of ca. 1600 mA h g−1. We attributed this phenomenon to the enhanced mechanical properties of the photo-cross-linked PAA-BP binder, which were evaluated using nanoindentation and swelling measurements.

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