Synthesis of Cathode and Anode Materials via Top-Down Approach for Li-ion Batteries

Battery Science and TechnologyCreating green energy solutions has become crucial to society. However, to achieve a clean and renewable energy system, significant developments must be made not only in energy conversion technologies (such as solar panels and wind turbines), but also in the feasibility and capabilities of stationary, electric-energy storage (EES). Many types of EES systems have been considered such as pumped hydroelectric storage, compressed air energy storage (CAES), flywheels, and electrochemical storage. Among them, electrochemical storage such as batteries has the advantage of being more efficient compared to other candidates because it is more suitable in scalability, efficiency, lifetime,discharge time, weight, and/or mobility of the system. Currently, lithium (Li)-ion rechargeable batteries have become very important in recent years due to their great promise as power source, but the batteries are limited by their materials’ performance. Accordingly, the development of high performance materials has been main focus in materials science research. Here, the achievements of cathode, anode,and current collector are described that they are synthesized via top-down approach to enhance their performance in Li-ion batteries. In cathode research, in spite of that there have been many reports dealing with nanostructured cathode materials, none of previous works have been reported the morphology transition of cathode materials via chemical etching. In this study, we found that a selective chemical etching method using PVP and AgNO3 is very promising for obtaining significantly improved electrochemical performance of the cathode materials even at high voltage range. This etching method spontaneously turns to layered morphology with a layer thickness of 10 nm. Furthermore, we found that the concurrent modification of layered LiCoO2 with a nanoscale Co3O4 coating layer by chemical etching to minimize the capacity loss and to maximize the rate capability of the cathode without the loss of the electrode density. In anode research, a novel architecture consisting of Si nanowires internally grown from pores in the etched graphite with high electrode density of 1.5 g/cm3 is introduced. In previous works, various nano-engineering concepts were introduced to overcome a volume related problem of Si during cycling.However, although these strategies exhibited a superior performance such as high capacity and good cycling stability, they cannot be satisfied with electrode density which is highly required to determine high energy density in practical approach. In this point of view, this work provides new strategy to design electrode material with practically required electrode density and high volumetric capacity. Simply, porous graphite as template for Si nanowires growth is designed via hydrogenation and Si nanowires are internally grown from pores in etched graphite via Vapor-Liquid-Solid process.Especially, porous graphite, which first is reported as top-down approach, plays a key role of good electrochemical performance in this work. In this system, not only porous graphite can offer free space to accommodate the volume change of Si nanowires, but also efficiently improve the electron transport between active materials. In current collector research, more advanced nanostructure anodes of uniform 3D Cu-Si core shell structured arrays with 250 and 500 nm diameter are produced using top-down processes. This nanostructured anodes improved in cycle stability and rate performance, even at 20 C rate. As a current collector, each Cu nanopillar substrate provides a high surface area for better mass accommodation of Si deposition while the space between them enhances the electrochemical reaction between the electrode and electrolyte and accommodates the volume change during cycling. In addition, because the fabrication of the Cu nanopillar substrate only involves conventional top-down processes, the nanopillars can be generated through a facile and fast process with control of the surface area and simple modulation of the nanopillar density or diameter. Remarkably, the well-patterned nanopillar substrate imparts a significantly enhanced connection between the current collector and active materials without a binder, and also provides free space to accommodate Si expansion without pulverization during cycling. As an additional part, owing to an introduction of devices that required a flexible energy storage,Li-ion batteries (LIBs) as a leading candidate have been widely considered due to high electrochemical performance. To approach a flexible property in LIBs, the system has highly required an electrode with flexible characteristic, therefore, graphene based composites has been strongly attractive due to the large surface area and electron transport with high mechanical strength. Also, as another field in anode material, vanadium sulfides (VS4) have been paid much attention due to high specific capacity and rate capability of lithium storage in these days. Accordingly, the composite consisting of grapheme and VS4 is synthesized and characterized to describe the mechanism for lithium storage and high electrochemical performance in LIBs.ope

Recent progress on nanostructured 4 v cathode materials for Li-ion batteries for mobile electronics

Mobile electronics have developed so rapidly that battery technology has hardly been able to keep pace. The increasing desire for lighter and thinner Li-ion batteries with higher capacities is a continuing and constant goal for in research. Achieving higher energy densities, which is mainly dependent on cathode materials, has become a critical issue in the development of new Li-ion batteries. In this review, we will outline the progress on nanostructured 4 V cathode materials of Li-ion batteries for mobile electronics, covering LiCoO2, LiNixCoyMn1-x-yO 2, LiMn2O4, LiNi0.5Mn 1.5O4 and Li-rich layered oxide materials. We aim to provide some scientific insights into the development of superior cathode materials by discussing the advantages of nanostructure, surface-coating, and other key properties.open2

The Relationship between Korean Parents’ Smartphone Addiction and That of Their Children: The Mediating Effects of Children’s Depression and Social Withdrawal

With the number of smartphone users growing around the world, children are using smartphones from an increasingly early age. Consequently, a significant number of children are being exposed to the risk of smartphone addiction, which is emerging as a serious social problem. Smartphone addiction can negatively impact children’s physical, cognitive, and social development. Previous studies have demonstrated that parental smartphone addiction influences that of their children. Therefore, this study explores the relationship between parental smartphone addiction and children’s smartphone addiction and the mediating effects of children’s depression and social withdrawal. Data are drawn from National Youth Policy Institute’s 2018 Korean Children and Youth Panel Survey. Respondents comprise 2011 fourth-grade elementary school students and their parents. Data were analyzed using SPSS version 21.0 and AMOS 21.0 software. Results show that the relationship between parental smartphone addiction and that of their children has a significantly positive mediating effect on children’s social withdrawal, but no such effect on children’s depression and there were no serial effects of children’s depression and social withdrawal. Consequently, educational programs that control parents’ smartphone usage, improve the parent–child relationship, and engender social sensitivity should be developed to reduce and prevent smartphone addiction among children

The Relationship between the Frequency of Breakfast Consumption, Conversation with Parents, and Somatic Symptoms in Children: A Three-Wave Latent Growth Model

Breakfast consumption is essential for children to generate energy for the day. Parents play an important role in children’s breakfast habits and spending time with parents during breakfast greatly influences children’s emotional development. Therefore, this study investigated the relationship between the frequency of children’s breakfast consumption, time spent in conversation with parents, and children’s somatic symptoms. Data were obtained from the Korea Children and Youth Panel Survey 2018 and were initially collected from fourth-grade elementary school students and followed up for three years. SPSS 21.0 and AMOS 21.0 software were used for data analysis. Multivariate latent growth modeling was applied to analyze the effect of the breakfast consumption frequency on children’s somatic symptoms and the mediating effect of parent–child conversation time on this relationship. Consequently, as children’s frequency of breakfast consumption increased, their somatic symptoms decreased. Furthermore, parent–child conversation time mediated the relationship between these two variables. Therefore, students, parents, and teachers should be educated about the importance of having breakfast and communicating with parents for students’ emotional health

Commercial and research battery technologies for electrical energy storage applications

Developing green energy solutions has become crucial to society. However, to develop a clean and renewable energy system, significant developments must be made, not only in energy conversion technologies (such as solar panels and wind turbines) but also regarding the feasibility and capabilities of stationary electrical energy storage (EES) systems. Many types of EES systems have been considered such as pumped hydroelectric storage (PHS), compressed air energy storage (CAES), flywheels, and electrochemical storage. Among them, electrochemical storage such as battery has the advantage of being more efficient compared to other candidates, because it is more suitable in terms of the scalability, efficiency, lifetime, discharge time, and weight and/or mobility of the system. Currently, rechargeable lithium ion batteries (LIBs) are the most successful portable electricity storage devices, but their use is limited to small electronic equipment. Using LIBs to store large amounts of electrical energy in stationary applications is limited, not only by performance but also by cost. Thus, a viable battery technology that can store large amounts of electrical energy in stationary applications is needed. In this review, well-developed and recent progress on the chemistry and design of batteries, as well as their effects on the electrochemical performance, is summarized and compared. In addition, the challenges that are yet to be solved and the possibilities for further improvements are explored. ??? 2015 Elsevier Ltd. All rights reservedclose2

Spindle-like Mesoporous alpha-Fe2O3 Anode Material Prepared from MOF Template for High-Rate Lithium Batteries

Spindle-like porous alpha-Fe2O3 was prepared from an iron-based metal organic framework (MOF) template. When tested as anode material for lithium batteries (LBs), this spindle-like porous alpha-Fe2O3 shows greatly enhanced performance of Li storage. The particle with a length and width of similar to 0.8 and similar to 0.4 mu m, respectively, was composed of clustered Fe2O3 nanoparticles with sizes of <20 nm. The capacity of the porous alpha-Fe2O3 retained 911 mAh g(-1) after 50 cycles at a rate of 0.2 C. Even when cycled at 10 C, comparable capacity of 424 mAh g(-1) could be achieved.close1307

Etched Graphite with Internally Grown Si Nanowires from Pores as an Anode for High Density Li-Ion Batteries

A novel architecture consisting of Si nanowires internally grown from porous graphite is synthesized by etching of graphite with a lamellar structure via a VLS (vapor-liquid-solid) process. This strategy gives the high electrode density of 1.5 g/cm3, which is comparable with practical anode of the Li-ion battery. Our product demonstrates a high volumetric capacity density of 1363 mAh/cm3 with 91% Coulombic efficiency and high rate capability of 568 mAh/cm3 even at a 5C rate. This good electrochemical performance allows porous graphite to offer free space to accommodate the volume change of Si nanowires during cycling and the electron transport to efficiently be improved between active materials.close16