Excess-Li Localization Triggers Chemical Irreversibility in Li- and Mn-Rich Layered Oxides

Li- and Mn-rich layered oxides (LMRs) have emerged as practically feasible cathode materials for high-energy-density Li-ion batteries due to their extra anionic redox behavior and market competitiveness. However, sluggish kinetics regions (<3.5 V vs Li/Li⁺) associated with anionic redox chemistry engender LMRs with chemical irreversibility (first-cycle irreversibility, poor rate properties, voltage fading), which limits their practical use. Herein, the structural origin of this chemical irreversibility is revealed through a comparative study involving Li_1.15Mn_0.51Co_0.17Ni_0.17O₂ with relatively localized and delocalized excess-Li in its lattice system. Operando fine-interval X-ray absorption spectroscopy is used to simultaneously observe the interplay between transition-metal–oxygen (TM-O) redox chemistry and TM migration behavior in real time. Density functional theory calculations show that excess-Li localization in the LMR structure attenuates TM-O covalency and stability, leading to overall chemical irreversibility. Hence, the delocalized excess-Li system is proposed as an alternative design for practically feasible LMR cathodes with restrained TM migration and sustainable O-redox chemistry.     

Metabolite profiling of ginsenoside Re in rat urine and faeces after oral administration

Following oral administration of ginsenoside Re, the compound and its metabolites were identified and quantified in rat urine and faeces by liquid chromatography coupled with triple quadrupole mass spectrometry (LC–MS/MS). Ginsenoside Re (200 mg/kg) was orally administered to rats by gastric intubation, and urine and faeces samples were then collected during the next 24 h using metabolic cages. Samples were prepared by solid phase extraction and analysed by LC–MS/MS. The precursor-product ion pairs used for LC–MS/MS analysis were: m/z 945 → 475 for ginsenoside Re, 799 → 637 for ginsenoside Rg1, 783 → 475 for ginsenoside Rg2, 637 → 475 for ginsenosides Rh1 and F1, 475 → 391 for protopanaxatriol, and 779 → 641 for digoxin (internal standard). The major ginsenosides excreted in urine were ginsenosides Re and Rg1, and only minimal amounts of ginsenosides Rg2 and Rh1 were found. Greater amounts of ginsenoside metabolites were detected in the faeces samples; biotransformation to ginsenoside Rg1 was predominant but further deglycosylated metabolites including ginsenoside F1 and protopanaxatriol were additionally detected. The total recovery of ginsenosides over 24 h was approximately 46%.     

Adsorption characteristics of arsenic and phosphate onto iron impregnated biochar derived from anaerobic granular sludge

Biological wastewater treatment produces biowaste (sludge), which contains a high portion of organic matter. The organic matter comes from microorganisms, and the biowaste can be converted into biochar, a carbon-rich, fine-grained, and porous substance. Granular sludge from upflow anaerobic sludge blanket contains more organic matter (80 wt% of dry matter) and carbon content (>50% of organic matter). In this study, iron impregnated biochar was prepared to remove arsenic (As) and phosphate, oxyanionic pollutants, from the aqueous phase. The iron impregnation of biochar was executed in a one-step by pyrolyzing the biowaste in the presence of Fe instead of conventional two-step, i.e., biochar production after then modification. The granular sludge biochar and activated sludge biochar did not adsorb at all As and phosphate. The adsorption capacity of granular sludge biochar was enhanced via iron impregnation, and the iron-impregnated granular sludge biochar removed 10.37 mg PO ₄ ^3- /g, 11.5 mg As(V)/g, and 6.1 mg As(III)/g, respectively. Therefore, the one-step process enhanced the adsorption capacity and reduced processing time for the adsorbent synthesis.     

Unveiling Nickel Chemistry in Stabilizing High‐Voltage Cobalt‐Rich Cathodes for Lithium‐Ion Batteries

A practical solution is presented to increase the stability of 4.45 V LiCoO₂ via high‐temperature Ni doping, without adding any extra synthesis step or cost. How a putative uniform bulk doping with highly soluble elements can profoundly modify the surface chemistry and structural stability is identified from systematic chemical and microstructural analyses. This modification has an electronic origin, where surface‐oxygen‐loss induced Co reduction that favors the tetrahedral site and causes damaging spinel phase formation is replaced by Ni reduction that favors octahedral site and creates a better cation‐mixed structure. The findings of this study point to previously unspecified surface effects on the electrochemical performance of battery electrode materials hidden behind an extensively practiced bulk doping strategy. The new understanding of complex surface chemistry is expected to help develop higher‐energy‐density cathode materials for rechargeable batteries.     

Rapid Inversion of Surface Charges in Heteroatom‐Doped Porous Carbon: A Route to Robust Electrochemical Desalination

Given that a considerably large population suffers from shortage of water, there are numerous on‐going efforts to turn seawater into freshwater, and electrochemical desalination processes—particularly capacitive deionization (CDI)—have gained significant attention due to their high energy efficiency and reliable performance. Meanwhile, carbonaceous electrode materials, which are most commonly used in CDI systems, have poor long‐term stability due to unfavorable interactions with oxygen in saline water. Herein, rapid and vigorous inversion of surface charges in heteroatom‐doped carbon electrodes, which leads to a robust operation of CDI with high desalination capacity, is reported for the first time. By carbonization of coffee wastes, nitrogen‐ and sulfur‐codoped activated carbon with hierarchical micro/mesopores are prepared in an environmentally‐friendly manner, and this carbon results in a significantly higher inverted capacity than that of various activated carbon counterparts in long‐term CDI operations, without any sign of drop in performance. Investigations on the changes in physicochemical properties of the electrodes during the inversion disclose the favorable roles of nitrogen and sulfur dopants, which can be summarized as enlarging the difference between the surface charges of the two electrodes by chemical interactions with oxygen in the anode and carbon in the cathode.     

Wire Optimization and Delay Reduction for High‐Performance on‐Chip Interconnection in GALS Systems

To address the wire complexity problem in large‐scale globally asynchronous, locally synchronous systems, a current‐mode ternary encoding scheme was devised for a two‐phase asynchronous protocol. However, for data transmission through a very long wire, few studies have been conducted on reducing the long propagation delay in current‐mode circuits. Hence, this paper proposes a current steering logic (CSL) that is able to minimize the long delay for the devised current‐mode ternary encoding scheme. The CSL creates pulse signals that charge or discharge the output signal in advance for a short period of time, and as a result, helps prevent a slack in the current signals. The encoder and decoder circuits employing the CSL are implemented using 0.25‐μm CMOS technology. The results of an HSPICE simulation show that the normal and optimal mode operations of the CSL achieve a delay reduction of 11.8% and 28.1%, respectively, when compared to the original scheme for a 10‐mm wire. They also reduce the power‐delay product by 9.6% and 22.5%, respectively, at a data rate of 100 Mb/s for the same wire length.     

Development of unfolding method to obtain pin-wise source strength distribution from PWR spent fuel assembly measurement

An unfolding method has been developed to obtain a pin-wise source strength distribution of a 14 × 14 pressurized water reactor (PWR) spent fuel assembly. Sixteen measured gamma dose rates at 16 control rod guide tubes of an assembly are unfolded to 179 pin-wise source strengths of the assembly. The method calculates and optimizes five coefficients of the quadratic fitting function for X–Y source strength distribution, iteratively. The pin-wise source strengths are obtained at the sixth iteration, with a maximum difference between two sequential iterations of about 0.2%. The relative distribution of pin-wise source strength from the unfolding is checked using a comparison with the design code (Westinghouse APA code). The result shows that the relative distribution from the unfolding and design code is consistent within a 5% difference. The absolute value of the pin-wise source strength is also checked by reproducing the dose rates at the measurement points. The result shows that the pin-wise source strengths from the unfolding reproduce the dose rates within a 2% difference.     

Whole cell biotransformation of major ginsenosides using Leuconostocs and Lactobacilli

Various strains of Lactobacillus and Leuconostoc species were evaluated to select the most promising strain to carry out transforming major ginsenosides into minor ginsenosides. Among the experimental lactic acid bacteria (LAB), Leuconostoc mesenteroides KFRI 690, Leuconostoc paramesenteroides KFRI 159, and Lactobacillus delbrueckii KCCM 35486 produced compound K from major ginsenosides precursors (Rb1, Rc, Rd, and F2). KFRI 690 showed the best transforming activity among them. Furthermore, these LABs could biotransform ginsenosides without disrupting the cell to release enzyme activity. The conversion ratio of Rb1 to compound K using KFRI 690 has been enhanced up to 97.8% by adding 2% sucrose into the culture medium. This is the first report on the production of compound K using whole cells of Leu. mesenteroides, Leu. paramesenteroides, and Lb. delbrueckii, which are food grade lactic acid bacteria.