Anode Study for Achieving Higher Energy Density in All-Solid-State Batteries

All-solid-state batteries (ASSBs) have gained lots of attention by both science and industry field. There are numerous benefits of adopting ASSB. First, because of inorganic solid-state electrolytes (SSEs), ASSBs have less safety concerns compared to the conventional liquid lithium-ion batteries (LIBs). Another reason is that, the energy density of ASSBs could exceeds that of LIBs with the premise of utilizing alloy-type or Li metal anode. Despite the extensive studies for decades, the alloy-type, especially Si anode, and Li metal failed to achieve reasonable cyclability up to the practical level. However, the recent studies shed light on excellent compatibility of argyrodite solid electrolyte, Li6PS5Cl, and anode-free (Li metal) anode and pure Si anode. First half of this dissertation is on the study of critical current density (CCD) of Li metal-ASSBs. The low CCD of Li metal-ASSBs hindered the practical operation of the cell, whereas inconsistent CCDs reported in academia. The variation of CCDs could be attributed to the various factors, such as temperature, solid electrolyte chemistry or pressure. The relationship between the fabrication pressure contact hold time of Li metal vs CCD is reported, elucidating the effect of controlled Li deformation on CCD. Further, the volumetric expansion of full cell configuration of Li metal-ASSB was mitigated to achieve higher CCDs at room temperature. Alloy-type Si anode was investigated in this thesis as well. Si-ASSBs have shown promising performance without continual solid-electrolyte interface (SEI) growth. However, the first cycle irreversible capacity loss yields low initial Coulombic efficiency (ICE) of Si, limiting the energy density. To address this, we adopt a prelithiaiton strategy to increase ICE and conductivity of Si-ASSBs. A significant ICE was observed for Li1Si anode paired with lithium cobalt oxide (LCO) cathode. A high areal capacity of up to 10 mAh cm-2 was attained using this Li1Si anode, suggesting that the prelithiation method may be suitable for high-loading next-generation all-solid-state batteries. The N/P ratio of Si in ASSBs showed peculiar behavior compared to liquid LIBs, which further broaden a usage of Si not only as anode but potentially as part of current collector. Overall, this dissertation offers an understanding of high-capacity anode for ASSBs which could lead to safe and high energy density cells, one step closer to commercialization

The Analysis of Antecedents for the Video Telephony Service Adoption: From the Value-Based Perspective

Korean Telecommunications Industry has a large scale market and boasts on high service quality and high technologies enough to provide the Video Telephony Service (VTS) satisfactorily. For many years, Korean telephone companies have been investing enormous sums to advertise their services widely and to allow their customers to change their cell phones for the third-generation (3G) devices indispensable for the service. However, despite their efforts, the VTS adoption rate in Korea is very low and it seems that customers seldom feel the necessity to use. From this viewpoint, it becomes necessary to find the antecedents influencing the intention to use for the VTS empirically. For this purpose, we proposed several hypotheses from the perspective of the Value-based Adoption Model (VAM). VAM is a conceptual model suggested to overcome some limitations of the Technology Acceptance Model (TAM) in explaining the adoption of new Information and Communication Technology (ICT) such as Mobile Internet where customers play the role of service consumer rather than simply technology users. We conducted a survey on 125 samples and found that customers perceive the value of VTS when they can recognize the service is functionally useful (Perceived Usefulness) and when they feel they can put themselves forward by using it (Self-Expression). On the other hand, the other factors including Technical Complexity, Privacy Concern and Perceived Price (Fee) don’t have statistically significant influences on the Perceived Value of VTS

Elucidating the Role of Prelithiation in Si-based Anodes for Interface Stabilization

Prelithiation as a facile and effective method to compensate the lithium inventory loss in the initial cycle has progressed considerably both on anode and cathode sides. However, much less research has been devoted to the prelithiation effect on the interface stabilization for long-term cycling of Si-based anodes. An in-depth quantitative analysis of the interface that forms during the prelithiation of SiOx is presented here and the results are compared with prelithiaton of Si anodes. Local structure probe combined with detailed electrochemical analysis reveals that a characteristic mosaic interface is formed on both prelithiated SiOx and Si anodes. This mosaic interface containing multiple lithium silicates phases, is fundamentally different from the solid electrolyte interface (SEI) formed without prelithiation. The ideal conductivity and mechanical properties of lithium silicates enable improved cycling stability of both prelithiated anodes. With a higher ratio of lithium silicates due to the oxygen participation, prelithiated SiO1.3 anode improves the initial coulombic efficiency to 94% in full cell and delivers good cycling retention (77%) after 200 cycles. The insights provided in this work can be used to further optimize high Si loading (>70% by weight) based anodes in future high energy density batteries

Design principles for enabling an anode-free sodium all-solid-state battery

Anode-free batteries possess the optimal cell architecture due to their reduced weight, volume and cost. However, their implementation has been limited by unstable anode morphological changes and anode–liquid electrolyte interface reactions. Here we show that an electrochemically stable solid electrolyte and the application of stack pressure can solve these issues by enabling the deposition of dense sodium metal. Furthermore, an aluminium current collector is found to achieve intimate solid–solid contact with the solid electrolyte, which allows highly reversible sodium plating and stripping at both high areal capacities and current densities, previously unobtainable with conventional aluminium foil. A sodium anode-free all-solid-state battery full cell is demonstrated with stable cycling for several hundred cycles. This cell architecture serves as a future direction for other battery chemistries to enable low-cost, high-energy-density and fast-charging batteries

Evaluating Electrolyte–Anode Interface Stability in Sodium All-Solid-State Batteries

All-solid-state batteries have recently gained considerable attention due to their potential improvements in safety, energy density, and cycle-life compared to conventional liquid electrolyte batteries. Sodium all-solid-state batteries also offer the potential to eliminate costly materials containing lithium, nickel, and cobalt, making them ideal for emerging grid energy storage applications. However, significant work is required to understand the persisting limitations and long-term cyclability of Na all-solid-state-based batteries. In this work, we demonstrate the importance of careful solid electrolyte selection for use against an alloy anode in Na all-solid-state batteries. Three emerging solid electrolyte material classes were chosen for this study: the chloride Na2.25Y0.25Zr0.75Cl6, sulfide Na3PS4, and borohydride Na2(B10H10)0.5(B12H12)0.5. Focused ion beam scanning electron microscopy (FIB-SEM) imaging, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) were utilized to characterize the evolution of the anode–electrolyte interface upon electrochemical cycling. The obtained results revealed that the interface stability is determined by both the intrinsic electrochemical stability of the solid electrolyte and the passivating properties of the formed interfacial products. With appropriate material selection for stability at the respective anode and cathode interfaces, stable cycling performance can be achieved for Na all-solid-state batteries

Benchmarking the reproducibility of all-solid-state battery cell performance

The interlaboratory comparability and reproducibility of all-solid-state battery cell cycling performance are poorly understood due to the lack of standardized set-ups and assembly parameters. This study quantifies the extent of this variability by providing commercially sourced battery materials—LiNi0.6Mn0.2Co0.2O2 for the positive electrode, Li6PS5Cl as the solid electrolyte and indium for the negative electrode—to 21 research groups. Each group was asked to use their own cell assembly protocol but follow a specific electrochemical protocol. The results show large variability in assembly and electrochemical performance, including differences in processing pressures, pressing durations and In-to-Li ratios. Despite this, an initial open circuit voltage of 2.5 and 2.7 V vs Li+/Li is a good predictor of successful cycling for cells using these electroactive materials. We suggest a set of parameters for reporting all-solid-state battery cycling results and advocate for reporting data in triplicate

Effect of Nb and Mo Addition on the Microstructure and Wear Behavior of Fe-Cr-B Based Metamorphic Alloy Coating Layer Manufactured by Plasma Spray Process

Fe-Cr-B-based metamorphic alloy coating layers were manufactured by plasma spray with a Fe-Cr-B-Mo-Nb composition (hereinafter, M+) powder. The microstructure and wear properties of the coating layers were investigated and compared with a metamorphic alloy coating layer fabricated with commercial m material. XRD analysis revealed that the M and M+ coating layers were composed of α-Fe, (Cr, Fe)2B, and some metallic glass phases. Wear test results showed that M+ coating layers had a superior wear resistance which had 1.48 times lower wear volume than M coating layers. Observations of the worn-out surfaces and cross-sections of the coating layers showed that M+ coating layer had relatively low oxides along the particle boundaries and it suppress a delamination behavior by the oxides

Outcomes after transabdominal cerclage in twin pregnancy with previous unsuccessful transvaginal cerclage.

Transabdominal cerclage (TAC) is reported to be effective for preventing preterm birth in women with unsuccessful transvaginal cerclage (TVC) history. However, TAC has rarely been performed in twin pregnancy given the lack of sufficient evidence and the technical difficulty of the operation. Thus, it is unclear whether TAC is an effective procedure for twin pregnancy in women with a history of unsuccessful TVC. The aim of this study is to compare the characteristics and pregnancy outcomes after TAC in twin pregnancy versus singleton pregnancy, to examine whether twin pregnancy is a risk factor for very preterm birth (before 32 weeks) after TAC, and to determine whether TAC is effective in preventing preterm birth in twin pregnancy. This single-center retrospective cohort study included women who underwent TAC because of unsuccessful TVC history between January 2007 and June 2018. Of 165 women who underwent TAC, 19 had twins and 146 had singletons. Our results showed that the neonatal survival rate improved dramatically when TAC was performed (15.4% (prior pregnancy) vs 94.0% (after TAC) in twins, p<0.01; 22.8% (prior pregnancy) vs 91.1% (after TAC) in singletons, p<0.01). Moreover, the risk of very preterm birth was significantly decreased after TAC in both groups (36/39 (92.3%) (prior pregnancy) vs 2/19 (10.5%) (after TAC) in twins, p<0.01; 290/337 (86.1%) (prior pregnancy) vs 17/146 (11.6%) (after TAC) in singletons, p<0.01). More advanced maternal age and history of prior preterm delivery between 26+0 and 36+6 weeks were independently associated with very preterm birth, whereas the presence of a twin pregnancy was not associated with very preterm birth on multivariate logistic regression analysis. These results suggest that TAC is associated with successful prevention of very preterm birth and improved neonatal survival rates in the absence of procedure-related major complications in women with twin pregnancy and previous unsuccessful TVC history