Deciphering the Formation and Accumulation of Solid-Electrolyte Interphases in Na and K Carbonate-Based Batteries.

The continuous solid-electrolyte interphase (SEI) accumulation has been blamed for the rapid capacity loss of carbon anodes in Na and K ethylene carbonate (EC)/diethyl carbonate (DEC) electrolytes, but the understanding of the SEI composition and its formation chemistry remains incomplete. Here, we explain this SEI accumulation as the continuous production of organic species in solution-phase reactions. By comparing the NMR spectra of SEIs and model compounds we synthesized, alkali metal ethyl carbonate (MEC, M = Na or K), long-chain alkali metal ethylene carbonate (LCMEC, M = Na or K), and poly(ethylene oxide) (PEO) oligomers with ethyl carbonate ending groups are identified in Na and K SEIs. These components can be continuously generated in a series of solution-phase nucleophilic reactions triggered by ethoxides. Compared with the Li SEI formation chemistry, the enhancement of the nucleophilicity of an intermediate should be the cause of continuous nucleophilic reactions in the Na and K cases.

Deregulation of the cell cycle and related microRNA expression induced by vinyl chloride monomer in the hepatocytes of rats.

Vinyl chloride (VC) is a confirmed human carcinogen associated with hepatocellular carcinoma and angiosarcoma. However, the role of microRNAs (miRNAs) in liver cell cycle changes under VC exposure remains unclear, which prevents research on the mechanism of VC-induced carcinogenesis. In this study, male rats were injected intraperitoneally with VC (0, 5, 25, and 125 mg/kg body weight) for 6, 8, and 12 weeks. Cell cycle analysis of liver cells, miRNA-222, miRNA-199a, miRNA-195, and miRNA-125b expression in the liver and serum, and target protein expression were performed at different time points. The results showed a higher percentage of hepatocytes in the G1/G0 and S phases at the end of 6 and 12 weeks of VC exposure, respectively. MiRNA-222 expression decreased initially and then increased, whereas miRNA-199a, miRNA-195, and miRNA-125b expression increased initially and then decreased, which corresponded with changes in cell cycle distribution and related target proteins expression (p27, cyclinA, cyclinD1, and CDK6). The corresponding expression levels of miRNAs in serum did not change. Dynamic changes in miR-222, miR-199a, miR-195, and miR-125b induced by VC can lead to cell cycle deregulation by affecting cell cycle-related proteins, and these miRNAs can serve as early biomarkers for malignant transformation caused by VC.

Prediction and Interpretability of Glass Transition Temperature of Homopolymers by Data-Augmented Graph Convolutional Neural Networks.

Establishing the structure-property relationship by machine learning (ML) models is extremely valuable for accelerating the molecular design of polymers. However, existing ML models for the polymers are subject to scarcity issues of training data and fewer variations of graph structures of molecules. In addition, limited works have explored the interpretability of ML models to infer the latent knowledge in the field of polymer science that could inspire ML-assisted molecular design. In this contribution, we integrate graph convolutional neural networks (GCNs) with data augmentation strategy to predict the glass transition temperature Tg of polymers. It is demonstrated that the data-augmented GCN model outperforms the conventional models and achieves a higher accuracy for the prediction of Tg despite a small amount of training data. Furthermore, taking advantage of molecular graph representations, the data-augmented GCN model has the capability to infer the importance of atoms or substructures from the understanding of Tg, which generally agrees with the experimental findings in the field of polymer science. The inferred knowledge of the GCN model is used to advise on the design of functional polymers with specific Tg. The data-augmented GCN model possesses prominent superiorities in the establishment of structure-property relationship and also provides an efficient way for accelerating the rational design of polymer molecules.

Key Factor Determining the Cyclic Stability of the Graphite Anode in Potassium-Ion Batteries.

Graphite is the most commonly used anode material for not only commercialized lithium-ion batteries (LIBs) but also the emerging potassium-ion batteries (PIBs). However, the graphite anode in PIBs using traditional dilute ester-based electrolyte systems shows obvious capacity fading, which is in contrast with the extraordinary cyclic stability in LIBs. More interestingly, the graphite in concentrated electrolytes for PIBs exhibits outstanding cyclic stability. Unfortunately, this significant difference in cycling performance has not raised concern up to now. In this work, by comparing the cyclic stability and graphitization degree of the graphite anode upon cycling, we reveal that the underlying mechanism of the capacity fading of the graphite anode in PIBs is not the larger volume expansion of graphite caused by the intercalation of potassium ions but the continual accumulation of the solid electrolyte interphase (SEI) on the surface of graphite. By X-ray photoelectron and nuclear magnetic resonance spectroscopies combined with chemical synthesis, it is concluded that the accumulation of the SEI may mainly come from the continual deposition of a kind of oligomer component, which blocks intercalation and deintercalation of potassium ions in graphite anodes. The designed SEI-cleaning experiment further verifies the above conclusion. This finding clarifies the crucial factor determining the cyclic stability of graphite and provides scientific guidance for application of the graphite anode for PIBs.

A highly concentrated electrolyte for high-efficiency potassium metal batteries.

We report a highly concentrated electrolyte consisting of 4 M potassium bis(fluorosulfonyl)imide (KFSI) in diethylene glycol dimethyl ether (DEGDME). This new electrolyte enables stable cycling of K metal anodes with a high CE (over 98% over 400 cycles), and excellent capacity retention (99.7% after 500 cycles) of K||potassium Prussian blue (KPB) batteries.

A Graphite Intercalation Composite as the Anode for the Potassium-Ion Oxygen Battery in a Concentrated Ether-Based Electrolyte.

Nowadays, alkali metal-oxygen batteries such as Li-, Na-, and K-O2 batteries have been investigated extensively because of their ultrahigh energy density. However, the oxygen crossover of oxygen batteries and the intrinsic drawbacks of the metal anodes (i.e., large volume changes and dendrite issues) have still been unsolved key problems. Here, we demonstrate a novel design of the K-ion oxygen battery using a graphite intercalation composite as the anode in a highly concentrated ether-based electrolyte. Instead of the metal K anode, the potassium graphite intercalation compound as the anode is depotassiated/potassiated in a binary form below 0.3 V (vs. K+/K); correspondingly, the discharged product KO2 is formed/decomposed at the carbon nanotube cathode, and an all-carbon full cell exhibits impressive cycling stability with a working voltage of 2.0 V. Furthermore, the utilization of graphite intercalation chemistry has been demonstrated to be applicable in Li-O2 batteries as well. Therefore, this study may provide a new strategy to resolve the key problems of the alkali metal-oxygen batteries.

Association between methylation of DNA damage response-related genes and DNA damage in hepatocytes of rats following subchronic exposure to vinyl chloride.

In the present study, we investigated the association between methylation of DNA damage response-related genes such as cyclin-dependent kinase inhibitor (CDKN)2A, Ras association (RalGDS/AF-6) domain family member (RASSF)1A, O6-methylguanine DNA methyltransferase (MGMT), Kirsten rat sarcoma viral oncogene homolog (KRAS), and spleen-associated tyrosine kinase (SYK) and DNA damage in hepatocytes of rats following subchronic exposure to vinyl chloride (VC). Sixty-four healthy rats were randomly divided into three VC exposure groups (5, 25, and 125 mg/kg) and an untreated negative control group (n = 16 each). VC was administered by intraperitoneal injection every other day for a total of three times a week. Eight randomly selected rats from each group were sacrificed at the end of 6 and 12 weeks, and liver tissue was harvested for the comet assay and for assessment of DNA methylation level and mRNA expression of related genes by PCR. Overall methylation levels in the genome of hepatocytes in VC-exposed rats were higher than those in the control group at 6 and 12 weeks (P < 0.05), although no differences were observed with regarding to dose (P > 0.05). After 12 weeks of exposure, differences in the methylation of RASSF1A and MGMT promoter regions were observed between the high-dose group and other groups (P < 0.05), whereas no differences were observed for the KRAS, SYK, and CDKN2A promoters (P > 0.05). These results suggest that DNA damage and increased genome-wide methylation are biomarkers for VC exposure and that RASSF1A and MGMT promoter methylation is related to the carcinogenic mechanism of VC.

Controllable Electrochemical Fabrication of KO2-Decorated Binder-Free Cathodes for Rechargeable Lithium-Oxygen Batteries.

Understanding the electrochemical property of superoxides in alkali metal oxygen batteries is critical for the design of a stable oxygen battery with high capacity and long cycle performance. In this work, a KO2-decorated binder-free cathode is fabricated by a simple and efficient electrochemical strategy. KO2 nanoparticles are uniformly coated on the carbon nanotube film (CNT-f) through a controllable discharge process in the K-O2 battery, and the KO2-decorated CNT-f is innovatively introduced into the Li-O2 battery as the O2 diffusion electrode. The Li-O2 battery based on the KO2-decorated CNT-f cathode can deliver enhanced discharge capacity, reduced charge overpotential, and more stable cycle performance compared with the battery in the absence of KO2. In situ formed KO2 particles on the surface of CNT-f cathode assist to form Li2O2 nanosheets in the Li-O2 battery, which contributes to the improvement of discharge capacity and cycle life. Interestingly, the analysis of KO2-decorated CNT-f cathodes, after discharge and cycle tests, reveals that the electrochemically synthesized KO2 seems not a conventional electrocatalyst but a partially dissolvable and decomposable promoter in Li-O2 batteries.

Development and application of a method for determination of nucleosides and nucleobases in Mactra veneriformis.

BACKGROUND: Mactra veneriformis, a typical marine bivalve mollusk, delicious sea food while low cost, is ubiquitous and abundant in Chinese coastal areas, especially in the coastal shoals of Jiangsu province. To our knowledge, previously reported analytical methods can not meet a set of quality control. OBJECTIVE: For the simultaneous determination of eight components (uridine, inosine, guanosine, thymidine, adenosine, xanthine, thymine and hypoxanthine) in M. veneriformis, a high performance liquid chromatography with UV detector method was established. MATERIALS AND METHODS: To develop the method, a reverse phase column, BioBasic-C18 (5 µm, 4.6 mm × 250 mm) was used. The mobile phase consisted of methanol and water using a gradient elution. The UV wavelength was set at 245 nm. The analysis conditions including extraction methods, extraction solvents, and HPLC parameters were optimized systematically for achieving good separation. Linearity, accuracy, repeatability and detection limit was revealed and showed good performance. RESULTS: The optimized HPLC method was successfully applied for the qualititation of 5 nucleosides namely, uridine, inosine, guanosine, thymidine, adenosine and 3 nucleobases namely, xanthine, thymine, hypoxanthine in M. veneriformis. CONCLUSION: A method with less time-consuming, more sensitive, and more precise was developed for the quantitative determination of nucleosides and nucleobases in M. veneriformis extractions. The established method might apply as an alternative approach for the quality assessment of M. veneriformis.

Simultaneous determination of eleven characteristic lignans in Schisandra chinensis by high-performance liquid chromatography.

BACKGROUND: Schisandra chinensis, one of the well-known traditional Chinese herbal medicines, is derived from the dry ripe fruits of Schisandra chinensis (Turcz.) Baill. according to the 9th China Pharmacopeia. Lignans are the main components isolated from extracts of S. chinensis and their content varies depending on where S. chinensis was collected. We have established a qualitative and quantitative method based on the bioactive lignans for control of the quality of S. chinensis from different sources. MATERIALS AND METHODS: To develop a high-performance liquid chromatography method, an Elite ODS C18 column (250 mm Χ 4.6 mm, 5µm) at a column temperature of 30°C and flow rate of 1.0ml/min using acetonitrile (A) and water (B) as the mobile phase with a linear gradient and the peaks were monitored at 217 nm. RESULTS: All calibration curves showed good linearity (r ≥ 0.9995) within test ranges. This method showed good repeatability for the quantification of these eleven components in S. chinensis with intra- and inter-day relative standard deviations less than 0.43% and 1.21%, respectively. In the recovery test, results of accuracy ranged from 99.51% to 101.31% with RSD values less than 2. CONCLUSION: The validated method can be successfully applied to quantify the eleven investigated components in 22 samples of S. chinensis from different sources.