Freeze-Vulnerable Plastic Crystal to Cryogenic Liquid Electrolyte for Lithium Batteries by Deep Freezing-Point Depression.

Low-Tf solvents (Tf = freezing point) are considered and employed for low-temperature lithium-ion battery (LIB) electrolytes to keep electrolytes in the liquid phase at low temperatures. Unfortunately, Tf is synchronized with Tb (boiling point) so low Tf brings Tb down and therefore discourages the thermal stability of electrolytes using low-Tf solvents. In this work, 1) the hot wing of LIB-working temperature by employing a high-Tb (inevitably high-Tf) solvent and 2) the cold wing by using a significant Tf depression is secured. Sulfolane is employed as the high-Tf (therefore, high-Tb) and high-Kf (Kf = cryoscopic constant) solvent since its mesomorphic state between solid and liquid. That abnormally and significantly decreases the enthalpy of fusion, and resultantly grants extremely high Kf at 66.4 K m-1. By employing sulfolane with 2 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the liquid-phase temperature window down to <-80 °C for the cold wing and simultaneously guaranteed its flash point at >+150 °C for the hot wing is successfully extended. LIB cells with lithium iron phosphate and lithium metal worked in a good stand with 2 m LiTFSI/sulfolane at room temperature, -30 °C as an ambient cold, -74 °C as a deep cold, and +80 °C as a deep hot.

What Makes a Photobattery Light-Rechargeable?

The demand for autonomous off-grid devices has led to the development of "photobatteries", which integrate light-energy harvesting and electrochemical energy storage in the same architecture. Despite several photobattery chemistries and designs being reported recently, there have been few insights into the physical conditions necessary for charge transfer between the photoelectrode and counter electrode. Here, we use a three-electrode photobattery with a dye-sensitized TiO2 photoelectrode, triiodide (I-/I3 -) catholyte, and anodes with varying intercalation potentials to confirm that photocharging is only feasible when the conduction band quasi-Fermi level (EFc) is positioned above the anode intercalation/plating potential. We also show that parasitic reactions after the battery is fully charged can be accelerated if the voltage of the battery and solar cell are not matched. The integration of multiple anodes in the same photobattery ensures well-controlled measurement conditions, allowing us to demonstrate the physical conditions necessary for charge transfer in photobatteries, which has been a topic of controversy in the field.

Influence of the Lithium-Ion Concentration in Electrolytes on the Performance of Dye-Sensitized Photorechargeable Batteries.

Dye-sensitized photorechargeable batteries (DSPBs) have recently gained attention for realizing energy recycling systems under dim light conditions. However, their performance under high storage efficiency (i.e., the capacity charged within a limited time) for practical application remains to be evaluated. Herein, we varied the lithium (Li)-ion concentration, which plays a dual role as energy charging and storage components, to obtain the optimized energy density of DSPBs. Electrochemical studies showed that the Li-ion concentration strongly affected the resistance characteristics of DSPBs. In particular, increasing the Li-ion concentration improved the output capacity and decreased the output voltage. Consequently, the energy density of the finely optimized DSPB improved from 8.73 to 12.64 mWh/cm3 when irradiated by a 1000-lx indoor light-emitting-diode lamp. These findings on the effects of Li-ion concentrations in electrolytes on the performance of DSPBs represent a step forward in realizing the practical application of DSPBs.

Cognitive function and activities of daily living in people affected by leprosy: A cross-sectional, population-based, case-control study.

OBJECTIVES: There has been controversy regarding whether or not people affected by leprosy have more cognitive dysfunction than healthy individuals. The purpose of this study was to assess cognitive functions and activities of daily living (ADL) in people affected by leprosy relative to a control population living in rural areas. MATERIALS AND METHODS: We assessed cognitive functions and ADL using the Korean Mini-Mental State Examination (K-MMSE), Korean Dementia Screening Questionnaire (KDSQ), and Seoul-Instrumental ADL (S-IADL). Higher scores of K-MMSE and lower scores of both KDSQ and S-IADL are indicative of better functioning. We assessed 224 persons living in Sorokdo who were affected by leprosy and 448 age- and gender-matched control subjects living in Namwon of the Chonbuk province. RESULTS: After adjusting for age, gender, and educational status, the K-MMSE score was found to be significantly higher in people affected by leprosy than in control subjects (23.14 ± 4.89 vs. 22.25 ± 4.62, respectively, P = 0.022). Items related to memory in the KDSQ showed no differences between the groups, but people affected by leprosy had a better score in division for other cognitive functions than controls. On items related to ADL in the KDSQ and S-IADL, people affected by leprosy performed significantly worse compared with controls. CONCLUSIONS: Our results suggest that although people affected by leprosy have a lower capacity of ADL, they may have better cognitive functions than normal controls.

Edge-exfoliated graphites for facile kinetics of delithiation.

As high rate charge and discharge characteristics of energy storage devices become more important with the market of electric vehicles intensively growing, the kinetics of lithiation or delithiation of electrode materials for lithium ion batteries require enhancement. Graphites, the most widely used anode materials, have a limited power density at high discharge rates, while their alternatives, such as silicon and transition metal oxides, show even inferior rate capability. This work was motivated from an idea of what if the edge opening of graphite was zipped more open to lithium ions in the electrolyte. By edge-selective functionalization, the peripheral d-spacing of graphite (d(0)) was locally controlled. Larger values of d(0) led to higher capacity especially at high discharge rates. Around 2-fold enhancement of capacity or energy density was achieved at 50C discharge rate from 110 to 190 mAh g(-1) by exfoliating graphite locally in its edge region. Also, the d(0) dependency of delithiation kinetics confirmed that the electrochemical step of Li(+) influx into or efflux out of the interlayer space of graphite is possibly the rate-determining step of lithiation or delithiation.

A hollow sphere secondary structure of LiFePO4 nanoparticles.

We report on the evolution of a hollow sphere secondary structure of spherical nanoparticles by a solubilization-reprecipitation mechanism based on the difference of solubility products (K(sp)) of two different precipitates. Carbon-coated nanoparticles of olivine structure LiFePO(4) served as the primary nano-blocks to build the secondary nano-architecture.