Improving Rate Performance of Encapsulating Lithium-Polysulfide Electrolytes for Practical Lithium-Sulfur Batteries.

The cycle life of high-energy-density lithium-sulfur (Li-S) batteries is severely plagued by the incessant parasitic reactions between Li metal anodes and reactive Li polysulfides (LiPSs). Encapsulating Li-polysulfide electrolyte (EPSE) emerges as an effective electrolyte design to mitigate the parasitic reactions kinetically. Nevertheless, the rate performance of Li-S batteries with EPSE is synchronously suppressed. Herein, the sacrifice in rate performance by EPSE is circumvented while mitigating parasitic reactions by employing hexyl methyl ether (HME) as a co-solvent. The specific capacity of Li-S batteries with HME-based EPSE is nearly not decreased at 0.1 C compared with conventional ether electrolytes. With an ultrathin Li metal anode (50 µm) and a high-areal-loading sulfur cathode (4.4 mgS cm-2 ), a longer cycle life of 113 cycles was achieved in HME-based EPSE compared with that of 65 cycles in conventional ether electrolytes at 0.1 C. Furthermore, both high energy density of 387 Wh kg-1 and stable cycle life of 27 cycles were achieved in a Li-S pouch cell (2.7 Ah). This work inspires the feasibility of regulating the solvation structure of LiPSs in EPSE for Li-S batteries with balanced performance.

An Organodiselenide Comediator to Facilitate Sulfur Redox Kinetics in Lithium-Sulfur Batteries with Encapsulating Lithium Polysulfide Electrolyte.

Lithium-sulfur (Li-S) batteries are regarded as promising high-energy-density energy storage devices. However, the cycling stability of Li-S batteries is restricted by the parasitic reactions between Li metal anodes and soluble lithium polysulfides (LiPSs). Encapsulating LiPS electrolyte (EPSE) can efficiently suppress the parasitic reactions but inevitably sacrifices the cathode sulfur redox kinetics. To address the above dilemma, a redox comediation strategy for EPSE is proposed to realize high-energy-density and long-cycling Li-S batteries. Concretely, dimethyl diselenide (DMDSe) is employed as an efficient redox comediator to facilitate the sulfur redox kinetics in Li-S batteries with EPSE. DMDSe enhances the liquid-liquid and liquid-solid conversion kinetics of LiPS in EPSE while maintains the ability to alleviate the anode parasitic reactions from LiPSs. Consequently, a Li-S pouch cell with a high energy density of 359 Wh kg-1 at cell level and stable 37 cycles is realized. This work provides an effective redox comediation strategy for EPSE to simultaneously achieve high energy density and long cycling stability in Li-S batteries and inspires rational integration of multi-strategies for practical working batteries.

Electrolyte Design for Improving Mechanical Stability of Solid Electrolyte Interphase in Lithium-Sulfur Batteries.

Practical lithium-sulfur (Li-S) batteries are severely plagued by the instability of solid electrolyte interphase (SEI) formed in routine ether electrolytes. Herein, an electrolyte with 1,3,5-trioxane (TO) and 1,2-dimethoxyethane (DME) as co-solvents is proposed to construct a high-mechanical-stability SEI by enriching organic components in Li-S batteries. The high-mechanical-stability SEI works compatibly in Li-S batteries. TO with high polymerization capability can preferentially decompose and form organic-rich SEI, strengthening mechanical stability of SEI, which mitigates crack and regeneration of SEI and reduces the consumption rate of active Li, Li polysulfides, and electrolytes. Meanwhile, DME ensures high specific capacity of S cathodes. Accordingly, the lifespan of Li-S batteries increases from 75 cycles in routine ether electrolyte to 216 cycles in TO-based electrolyte. Furthermore, a 417 Wh kg-1 Li-S pouch cell undergoes 20 cycles. This work provides an emerging electrolyte design for practical Li-S batteries.

Soft Electrodes for Electrochemical and Electrophysiological Monitoring of Beating Cardiomyocytes.

Many cells in vivo have their inherent motions, which involve numerous biochemical and biophysical signals synergistically regulating cell behavior and function. However, existing methods offer little information about the concurrently chemical and physical responses of dynamically pulsing cells. Here, we report a soft electrode with an electrospun poly(3,4-ethylenedioxythiophene) (PEDOT)-based nanomesh to fully comply with spontaneous motions of cells. Moreover, this electrode demonstrated excellent electrical conductivity, electrochemical performance and cellular biocompatibility. Cardiomyocytes cultured thereon exhibited autonomous and rhythmic contractility, and synchronously induced mechanical deformation of the underlying electrode, which allowed real-time monitoring of nitric oxide release and electrophysiological activity of cardiomyocytes. This work provides a promising way toward recording chemical and electrical signals of biological systems with their natural motions.

Oligo(ethylene glycol)-Functionalized Ratiometric Fluorescent Probe for the Detection of Hydrazine in Vitro and in Vivo.

Hydrazine induced toxicity causes serious harm to the health of humans. The detection of N2H4 in vitro and in vivo has attracted a great deal of attention, especially in the context of fluorescent probes. Although some fluorescent N2H4 probes have been reported, only a few operate in purely aqueous media and, as a result, require the use of organic cosolvents which hinders their use in analysis of real samples. In addition, most of the current N2H4 probes are either "off-on" or "on-off" types, in which it is difficult to eliminate interference from background fluorescence commonly occurring in in vitro and in vivo systems. Furthermore, some probes are unable to differentiate hydrazine from other organic amines. To address the above problems, we developed a novel oligo(ethylene glycol)-functionalized fluorescent probe for the detection of N2H4. The probe, which has a donor-π-acceptor (D-π-A)-type structure, is water-soluble, and it can be utilized to selectively detect N2H4 in both colorimetric and ratiometric mode. Furthermore, the probe is able to differentiate hydrazine from other organic amines and can be used to detect hydrazine vapor and for imaging A549 cells and zebrafish.

Overexpression of TaSIM provides increased drought stress tolerance in transgenic Arabidopsis.

Drought is the most serious meteorological disaster affecting wheat production. Members of the R2R3-MYB gene subfamily play a crucial role in the regulation of the wheat drought stress response. In this study, the function of polyethylene glycol (PEG)-induced expression of the wheat R2R3-MYB gene TaSIM in response to drought stress was characterized. ß-Glucuronidase (GUS) histochemical staining revealed that the TaSIM promoter can drive the expression of the GUS gene in the flowers, roots, stems and rosette leaves. Moreover, TaSIM was expressed in the stamens, pistils, roots, stems and leaves of wheat. The TaSIM promoter contains a known stress-responsive cis-acting element and is inducible by stress, PEG and abscisic acid (ABA). Under drought stress, compared with wild-type (WT) Arabidopsis, transgenic Arabidopsis overexpressing TaSIM presented significantly lower leaf water loss rates and increased survival. Moreover, the content of soluble sugars and proline and the expression of stress-related genes (RD29A and RD22) in transgenic Arabidopsis overexpressing TaSIM were higher than those in WT Arabidopsis under drought stress. Our results indicate that TaSIM plays a positive role in the drought stress response and can be used as a candidate gene for the genetic engineering of wheat drought resistance.

Unveiling the Reaction Mystery Between Lithium Polysulfides and Lithium Metal Anode in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are widely regarded as one of the most promising next-generation high-energy-density energy storage devices. However, soluble lithium polysulfides (LiPSs) corrode Li metal and deteriorate the cycling stability of Li-S batteries. Understanding the reaction mechanism between LiPSs and Li metal anode is imperative. Herein, the reaction rate and products of LiPSs with Li metal anode, the composition and structure of the as-generated solid electrolyte interphase (SEI), and the mechanism of lithium nitrate (LiNO3) additives for inhibiting the corrosion reactions are systematically unveiled. Concretely, LiPSs react with Li metal anode more rapidly than Li salt and generate a Li2S-rich SEI. The Li2S-rich SEI is highly reactive with LiPSs, which exacerbates the formation of dendritic Li and the continuous corrosion of active Li. LiNO3 functions dominantly by modulating the solvation structure of LiPSs and inherently reducing the reactivity of LiPSs, rather than the conventional understanding of LiNO3 participating in the formation of SEI. This work reveals the reaction mechanism between LiPSs and Li metal anode and inspires rational regulating of the solvation structure of LiPSs for stabilizing Li metal anode in Li-S batteries.

Nanofiber-based Stretchable Electrodes for Oriented Culture and Mechanotransduction Monitoring of Smooth Muscle Cells.

Vascular smooth muscle cells (SMCs) are circumferentially oriented perpendicular to the blood vessel and maintain the contractile phenotype in physiological conditions. They can sense the mechanical forces of blood vessels expanding and contracting and convert them into biochemical signals to regulate vascular homeostasis. However, the real-time monitoring of mechanically evoked biochemical response while maintaining SMC oriented growth remains an important challenge. Herein, we developed a stretchable electrochemical sensor by electrospinning aligned and elastic polyurethane (PU) nanofibers on the surface of PDMS film and further modification of conductive polymer PEDOT:PSS-LiTFSI-CoPc (PPLC) on the nanofibers (denoted as PPLC/PU/PDMS). The aligned nanofibers on the electrode surface could guide the oriented growth of SMCs and maintain the contractile phenotype, and the modification of PPLC endowed the electrode with good electrochemical sensing performance and stability under mechanical deformation. By culturing cells on the electrode surface, the oriented growth of SMCs and real-time monitoring of stretch-induced H2O2 release were achieved. On this basis, the changes of H2O2 level released by SMCs under the pathology (hypertension) and intervention of natural product resveratrol were quantitatively monitored, which will be helpful to further understand the occurrence and development of vascular-related diseases and the mechanisms of pharmaceutical intervention.

Anode Material Options Toward 500 Wh kg-1 Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) battery is identified as one of the most promising next-generation energy storage systems due to its ultra-high theoretical energy density up to 2600 Wh kg-1 . However, Li metal anode suffers from dramatic volume change during cycling, continuous corrosion by polysulfide electrolyte, and dendrite formation, rendering limited cycling lifespan. Considering Li metal anode as a double-edged sword that contributes to ultrahigh energy density as well as limited cycling lifespan, it is necessary to evaluate Li-based alloy as anode materials to substitute Li metal for high-performance Li-S batteries. In this contribution, the authors systematically evaluate the potential and feasibility of using Li metal or Li-based alloys to construct Li-S batteries with an actual energy density of 500 Wh kg-1 . A quantitative analysis method is proposed by evaluating the required amount of electrolyte for a targeted energy density. Based on a three-level (ideal material level, practical electrode level, and pouch cell level) analysis, highly lithiated lithium-magnesium (Li-Mg) alloy is capable to achieve 500 Wh kg-1 Li-S batteries besides Li metal. Accordingly, research on Li-Mg and other Li-based alloys are reviewed to inspire a promising pathway to realize high-energy-density and long-cycling Li-S batteries.

Weakening the Solvating Power of Solvents to Encapsulate Lithium Polysulfides Enables Long-Cycling Lithium-Sulfur Batteries.

Long cycling lifespan is a prerequisite for practical lithium-sulfur batteries yet is restricted by side reactions between soluble polysulfides and the lithium-metal anode. The regulation on solvation structure of polysulfides renders encapsulating polysulfides electrolytes (EPSE) as a promising solution to suppress the parasitic reactions. The solvating power of the solvents in the outer solvent shell of lithium polysulfides is critical for the encapsulation effect of EPSE. Herein, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) is demonstrated as a superior outer-shell solvent to construct EPSE. Based on the large steric hindrance of the fluorohydrocarbon chains, the electron-withdrawing perfluoro segment (CF2  further endows HFE with prominently weak solvating power. The HFE-EPSE improves the lifespan from 54 to 135 cycles for lithium-sulfur batteries with an ultrathin lithium-metal anode (50 µm) and high-areal-loading sulfur cathode (4.4 mg cm-2 ). Furthermore, a 334 Wh kg-1 lithium-sulfur pouch cell (2.4 Ah level) with HFE-EPSE stably undergoes 25 cycles. This work demonstrates the role of weakening solvating power of outer-shell solvents to construct superior EPSE and inspires the significance of the solvation chemistry of polysulfides to achieve practical lithium-sulfur batteries.