A Polymer-Rich Quaternary Composite Solid Electrolyte for Lithium Batteries

All-solid-state batteries continue to grow as an alternative to replace the traditional liquid-based ones not only because they provide increased safety but also higher power and energy densities. However, current solid-state electrolytes are either ceramics that are brittle but highly conducting (e.g. Li0.33La0.55TiO3, LLTO) or polymer electrolytes that are poorly conducting but form flexible films with desired mechanical properties (e.g. Poly(ethylene oxide):Lithium bis(trifluoromethanesulfonyl)imide, PEO:LiTFSI). In this work, we have developed quaternary composite solid-state electrolytes (CSEs) to combine the benefits of the two types along with Succinonitrile (SN) as a solid plasticizer. CSEs with different compositions have been fully characterized over the whole compositional range. Guided by neural network simulation results it has been found that a polymer-rich CSE film gives the optimal ionic conductivity (>10−3 S cm−1 at 55 °C) and mechanical properties (Tensile strength of 16.1 MPa; Elongation-at-break of 2360%). Our solid-state coin-type cell which employs our in-house made cathode shows good cycling performance at C/20 and 55 °C maintaining specific discharge capacity at 143.2 mAh g−1 after 30 cycles. This new approach of formulating quaternary CSEs is proven to give the best combination of properties and should be universal and be applied to other CSEs with different chemistry

Prevalence and risk factors of Helicobacter pylori infection in Korea: Nationwide multicenter study over 13 years

Background : The aim of this study was to evaluate the time trend of seropositivity of Helicobacter pylori (H. pylori) over the period of 13 years in an asymptomatic Korean population, and investigate associated risk factors. Methods : This cross-sectional nationwide multicentre study surveyed anti-H. pylori IgG antibodies in 19,272 health check-up subjects (aged [greater than and equal to]16 years) in 2011. Risk factors for H. pylori infection were investigated using logistic regression. Seropositivity in asymptomatic subjects without H. pylori eradication was compared between the years 1998 and 2005. Birth cohort effects were also evaluated. Results : After exclusion of subjects with a history of H. pylori eradication therapy (n = 3,712, 19.3%) and gastric symptoms (n = 4,764, 24.7%), the seroprevalence of H. pylori infection was 54.4% in 10,796 subjects. This was significantly lower than the seroprevalence of 59.6% in 2005 and that of 66.9% in 1998, and this decrease of seropositivity of H. pylori became widespread across all ages and in most areas of the country. This decreasing trend could be explained by cohort analysis. All younger birth cohorts had a lower seroprevalence of H. pylori than older birth cohorts at the same age. Decreased seroprevalence within the same birth cohorts also accounted for this phenomenon. Clinical risk factors of H. pylori infection were higher cholesterol level ([greater than and equal to] 240 mg/dl) (OR = 1.33; 95% CI = 1.14-1.54), male gender, older age, low income, and residence in a rural area. Conclusions : A decreasing trend of H. pylori seroprevalence due to a birth cohort effect requires further studies on its related human host factors as well as socio-economic and hygienic factors. In addition, the relationship between H. pylori infection and high cholesterol level needs more investigation regarding underlying pathogenesis.This work was supported by the National Research Foundation of Korea (NRF) grant for the Global Core Research Center (GCRC) funded by the Korea government (MSIP) (No. 2011-0030001)Peer Reviewe

Organic Template-Assisted Synthesis & Characterization of Active Materials for Li-ion Batteries

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs

Electrochemical Performance of Titania 3D Nanonetwork Electrodes Induced by Pulse Ionization at Varied Pulse Repetitions

Pulse ionized titania 3D-nanonetworks (T3DN) are emerging materials for fabricating binder-free and carbon-free electrodes for electrochemical energy storage devices. In this article, we investigate the effect of the one of the most important fabrication parameters, pulse frequency, for optimizing supercapacitor efficiency. A series of coin cell batteries with laser-induced electrodes was fabricated; the effect of pulse frequency on oxidation levels and material properties was studied using both experimental and theoretical analysis. Also, detailed electrochemical tests including cyclic voltammetry (CV), charge/discharge, and electrochemical impedance spectroscopy (EIS) were conducted to better understand the effect of pulse frequency on the electrochemical performance of the fabricated devices. The results show that at a frequency of 600 kHz, more T3DN were observed due to the higher temperature and stabler formation of the plasma plume, which resulted in better performance of the fabricated supercapacitors; specific capacitances of samples fabricated at 600 kHz and 1200 kHz were calculated to be 59.85 and 54.39 mF/g at 500 mV/s, respectively

A high capacity silicon-graphite composite as anode for lithium-ion batteries using low content amorphous silicon and compatible binders

In this study, silicon-graphite composites were prepared and investigated as anode materials for Li-ion batteries with small amounts of silicon and different binders. The silicon powders were prepared by ball-milling crystalline silicon for 100 h and 200 h. After 200 h, an average silicon particle size of 0.73 \u3bcm was obtained and XRD measurements confirmed the formation of an amorphous powder embedded within nanocrystalline regions. XPS analysis of the silicon samples showed that silicon particles were covered with a native silicon oxide layer that grows during ball-milling. Battery cycling of the silicon powders in half cells showed that the powder ball milled for 200 h gave the lowest first-cycle irreversible capacity and the highest reversible capacity reaching over 500 mA h g-1 after 50 cycles at C/12. Composites were made using graphite and only 5 wt% silicon powders. The silicon was found to be uniformly dispersed into the composites as evidenced by X-ray mapping and SEM. When tested in half cells using different binders, it was found that the polyetherimide binder showed the highest capacity reaching 514 mA h g -1 after 350 cycles at C/12, which is 1.6 times greater than commercial graphite anode. High rate cycling showed good capacity retention reaching half the capacity at 5 C.Peer reviewed: YesNRC publication: Ye

On the Current and Future Outlook of Battery Chemistries for Electric Vehicles—Mini Review

As the electrification of the transportation industry is accelerating, the energy storage markets are trying to secure more reliable and environmentally benign materials. Advanced materials are the key performance enablers of batteries as well as a key element determining the cost structure, environmental impact, and recyclability of battery cells. In this review, we analyzed the state-of-the-art cell chemistries and active electrode and electrolyte materials for electric vehicles batteries, which we believe will dominate the battery chemistry landscape in the next decade. We believe that major breakthroughs and innovations in electrode materials such as high-nickel cathodes and silicon and metallic lithium anodes, along with novel liquid electrolyte formulations and solid-state electrolytes, will significantly improve the specific capacity of lithium batteries and reduce their cost, leading to accelerated mass-market penetration of EVs

Highly ordered LiFePO4 cathode material for Li-ion batteries templated by surfactant-modified polystyrene colloidal crystals

An organic template assisted synthesis was developed to obtain highly ordered porous LiFePO4 cathode material. The developed synthesis enabled the use of polystyrene (PS) as template by modifying its surface with a surfactant (Brij 78) to render it hydrophilic. The material was synthesized in high yield and purity as confirmed by X-ray powder diffraction. The TEM and SEM images clearly confirmed the presence of a highly ordered porous structure and the latter showed that the structure has an average pore diameter of 400 nm and a wall thickness and depth of ~100 nm. Thermal scans and elemental analysis showed that the material contains a high amount of carbon reaching 23-28% by weight. The surface area was calculated using the BET method and found to be 7.71m(to the power of 2)g(to the power of-1). Li/LiFePO4 half cells were tested and gave satisfactory discharge capacities; an initial capacity [158mAhg(to the power of -1)] close to the theoretical value and recoverable capacities at high C-rates (2-5 C).Peer reviewed: YesNRC publication: Ye