Rational Regulation of High-Voltage Stability in Potassium Layered Oxide Cathodes.

Layered oxide cathode materials may undergo irreversible oxygen loss and severe phase transitions during high voltage cycling and may be susceptible to transition metal dissolution, adversely affecting their electrochemical performance. Here, to address these challenges, we propose synergistic doping of nonmetallic elements and in situ electrochemical diffusion as potential solution strategies. Among them, the distribution of the nonmetallic element fluorine within the material can be regulated by doping boron, thereby suppressing manganese dissolution through surface enrichment of fluorine. Furthermore, in situ electrochemical diffusion of fluorine from the surface into the bulk of the materials after charging reduces the energy barrier of potassium ion diffusion while effectively inhibiting irreversible oxygen loss under high voltage. The modified K0.5Mn0.83Mg0.1Ti0.05B0.02F0.1O1.9 layered oxide cathode exhibits a high capacity of 147 mAh g-1 at 50 mA g-1 and a long cycle life of 2200 cycles at 500 mA g-1. This work demonstrates the efficacy of synergistic doping and in situ electrochemical diffusion of nonmetallic elements and provides valuable insights for optimizing rechargeable battery materials.

Less is More: Underlying Mechanism of Zn Electrode Long-Term Stability using Sodium L-Ascorbate as Electrolyte Additive.

Structured passivation layers and hydrated Zn2+ solvation structure strongly influence Zn depositions on Zn electrodes and then the cycle life and electrochemical performance of aqueous zinc ion batteries. To achieve these, the electrolyte additive of sodium L-ascorbate (Ass) is introduced into aqueous zinc sulfate (ZnSO4 , ZS) electrolyte solutions. Combined experimental characterizations with theoretical calculations, the unique passivation layers with vertical arrayed micro-nano structure are clearly observed, as well as the hydrated Zn2+ solvation structure is changed by replacing two ligand water molecules with As- , thus regulating the wettability and interfacial electric field intensity of Zn surfaces, facilitating rapid ionic diffusions within electrolytes and electrodes together with the inhibited side reactions and uniform depositions of Zn2+ . When tested in Zn||Zn symmetric cell, the electrolyte containing Ass is extraordinarily stably operated for the long time ≈3700 h at both 1 mA cm-2 and 1 mAh cm-2 . In Zn||MnO2 full coin cells, the energy density can still maintain as high as ≈184 Wh kg-1 at the power density high up to 2 kW kg-1 , as well as the capacity retention can reach up to 80.5% even after 1000 cycles at 2 A g-1 , which are substantially superior to the control cells.

Having Your Cake and Eating It Too: Electrode Processing Approach Improves Safety and Electrochemical Performance of Lithium-Ion Batteries.

A layered Li[NixCoyMn1-x-y]O2 (NCM)-based cathode is preferred for its high theoretical specific capacity. However, the two main issues that limit its practical application are severe safety issues and excessive capacity decay. A new electrode processing approach is proposed to synergistically enhance the electrochemical and safety performance. The polyimide's (PI) precursor is spin-coated on the LiNi0.5Co0.2Mn0.3O2 (NCM523) electrode sheet, and the homogeneous sulfonated PI layer is in situ produced by thermal imidization reaction. The PI-spin coated (PSC) layer provides improvements in capacity retention (86.47% vs 53.77% after 150 cycles at 1 C) and rate performance (99.21% enhancement at 5 C) as demonstrated by the NCM523-PSC||Li half-cell. The NCM523-PSC||graphite pouch full cell proves enhanced capacity retention (76.62% vs 58.58% after 500 cycles at 0.5 C) as well. The thermal safety of the NCM523-PSC cathode-based pouch cell is also significantly improved, with the critical temperature of thermal safety T1 (the beginning temperature of obvious self-heating temperature) and thermal runaway temperature T2 increased by 60.18 and 44.59 °C, respectively. Mechanistic studies show that the PSC layer has multiple effects as a passivation layer such as isolation of electrode-electrolyte contact, oxygen release suppression, solvation structure tuning, and the decomposition of carbonate solvents as well as LiPF6 inhibition. This work provides a new path for a cost-effective and scalable design of electrode decoration with synergistic safety-electrochemical kinetics enhancement.

Phase-engineered cathode for super-stable potassium storage.

The crystal phase structure of cathode material plays an important role in the cell performance. During cycling, the cathode material experiences immense stress due to phase transformation, resulting in capacity degradation. Here, we show phase-engineered VO2 as an improved potassium-ion battery cathode; specifically, the amorphous VO2 exhibits superior K storage ability, while the crystalline M phase VO2 cannot even store K+ ions stably. In contrast to other crystal phases, amorphous VO2 exhibits alleviated volume variation and improved electrochemical performance, leading to a maximum capacity of 111 mAh g-1 delivered at 20 mA g-1 and over 8 months of operation with good coulombic efficiency at 100 mA g-1. The capacity retention reaches 80% after 8500 cycles at 500 mA g-1. This work illustrates the effectiveness and superiority of phase engineering and provides meaningful insights into material optimization for rechargeable batteries.

Mechanical Insights into the Electrochemical Properties of Thornlike Micro-/Nanostructures of PDA@MnO2@NMC Composites in Aqueous Zn Ion Batteries.

As emerging energy storage devices, aqueous zinc ion batteries (AZIBs) with outstanding advantages of high safety, high energy density, and environmental friendliness have attracted much research interest. Herein, the favorable thornlike MnO2 micro-/nanostructures (PDA@MnO2@NMC) are rationally constructed by the incorporation of both carbon substrates (NMC) and polydopamine (PDA) surface modifications. Ex situ X-ray diffraction and Raman characteristics show the formation of MnOOH and ZnMn2O4 products, corresponding to H+ and Zn2+ insertions in two discharge platforms. Density functional theory (DFT) calculations also demonstrate that PDA can firmly anchor onto MnO2 surfaces and prevent the dissolution of MnOOH. In addition, PDA with more hydrophilic groups can capture more H+ together with the increased surface capacitance and the extension of the first discharge platform, while the NMC carbon substrate can provide abundant active sites for the overgrown MnO2 nanowires, improve the conductivity, and promote fast ion and electron transportations. Further, electrochemical impedance spectroscopy (EIS) and GITT results show that the ohmic resistance of PDA@MnO2@NMC decreases to almost half and, in particular, the ion diffusion coefficient increases more than 30 times of pure MnO2. As such, PDA@MnO2@NMC in the AZIB cathode exhibits excellent electrochemical performance compared to the pure MnO2, which is expected to have favorable competitiveness in energy storage devices.

One Stone for Multiple Birds: A Versatile Cross-Linked Poly(dimethyl siloxane) Binder Boosts Cycling Life and Rate Capability of an NCM 523 Cathode at 4.6 V.

Increasing working voltage is a promising way to increase the energy density of lithium-ion batteries. Cycling and rate performance deteriorated due to excessive electrolyte decomposition and uncontrolled formation of a cathode-electrolyte interface (CEI) layer at a high voltage. A new concept is proposed to construct a high-voltage-stable electrode-electrolyte interface. An elastomeric poly(dimethyl siloxane) (PDMS) binder is incorporated into the electrode to modify the LiNi0.5Co0.2Mn0.3O2 (NCM 523) particle surface via an in situ cross-linking reaction between hydroxy-terminated PDMS and methyl trimethoxy silane promoted by moisture at ambient conditions (MPDMS). Improved electrochemical performance is achieved with the MPDMS binder in terms of reversible capacity (201 vs 185 mAh·g-1 at 0.2C), capacity retention (80 vs 68%, after 300 cycles at 1C), and rate performance (55.6% increase at 5C), as demonstrated by the NCM 523||Li half-cell. The NCM 523||graphite full-cell also shows improved performance at 4.6 V (147 vs 128 mAh·g-1, 82 vs 76%, after 200 cycles at 1C). The mechanism studies indicate that MPDMS exerts multiple effects, including cathode surface passivation, solvation structure tuning, electrolyte uptake enhancement, and mechanical stress relief. This work provides an inspiring route to realize high-voltage application of lithium-ion battery technology.

Unraveling Sequence Effect on Glass Transition Temperatures of Discrete Unconjugated Oligomers.

Sequence plays a critical role in enabling unique properties and functions of natural biomolecules, which has promoted the rapid advancement of synthetic sequence-defined polymers in recent decades. Particularly, investigation of short chain sequence-defined oligomers (also called discrete oligomers) on their properties has become a hot topic. However, most studies have focused on discrete oligomers with conjugated structures. In contrast, unconjugated oligomers remain relatively underexplored. In this study, three pairs of discrete oligomers with the same composition but different sequence for each pair are employed for investigating their glass transition temperatures (Tg s). The resultant Tg s of sequenced oligomers in each pair are found to be significantly different (up to 11.6 °C), attributable to variations in molecular packing as demonstrated by molecular dynamics and density function theory simulations. Intermolecular interaction is demonstrated to have less impact on Tg s than intramolecular interaction. The mechanistic investigation into two model dimers suggests that monomer sequence caused the difference in intramolecular rotational flexibility of the sequenced oligomers. In addition, despite having different monomer sequence and Tg s, the oligomers have very similar solubility parameters, which supports their potential use as effective oligomeric plasticizers to tune the Tg s of bulk polymer materials.

Comparative study on the intestinal absorption of three gastrodin analogues via the glucose transport pathway.

Gastrodin is the main active constituent of Tianma, a famous traditional Chinese herbal medicine. Our previous research has found that gastrodin is absorbed rapidly in the intestine by the sodium-dependent glucose transporter 1 (SGLT1). In the current report, gastrodin is the best glycoside compound absorbed via the glucose transport pathway. This study aimed to investigate the effect of the slight difference in chemical structure on the drug intestinal absorption via the glucose transport pathway. Traditional biopharmaceutical and computer-aided molecular docking methods were used to evaluate the intestinal absorption characteristics of three gastrodin analogues, namely, salicin, arbutin and 4-methoxyphenyl-ß-D-glucoside (4-MG). The oil-water partition coefficient (logP) experiments showed that the logP values of the gastrodin analogues followed the order: 4-MG > salicin > arbutin. In vitro Caco-2 cell transport experiments demonstrated that the apparent permeability coefficient (Papp) value of arbutin was higher than those of salicin and 4-MG. In situ single-pass intestinal perfusion experiments showed that the absorption of arbutin and 4-MG was better than that of salicin and that the absorption of the three compounds in the colon was lower than that in the small intestine. Quantitative real-time polymerase chain reaction results confirmed that the SGLT1 mRNA expression in the small intestine of rats was obviously higher than that in the colon of rats. In vivo pharmacokinetic experiments demonstrated that the oral bioavailability of salicin was lower than those of arbutin and 4-MG. In vitro and in vivo experiments showed that glucose or phlorizin (SGLT1 inhibitor) could decrease the intestinal absorption of the three compounds. Contrary to the above biopharmaceutical experiments, the computer-aided molecular docking test showed that the affinity of salicin to the vSGLT receptor was stronger than those of arbutin and 4-MG. In conclusion, the SGLT1 can facilitate the intestinal absorption of salicin, arbutin and 4-MG, and the slight difference in chemical structure can affect absorption.

Optimization of lipid materials in the formulation of S-carvedilol self-microemulsifying drug-delivery systems.

OBJECTIVES: The blocking effect of S-carvedilol (S-CAR) on the beta-adrenoceptor is about 100 times stronger than that of the right-handed conformation. However, further development is restricted because of its poor bioavailability caused by its low solubility and high first-pass effect. In the study, S-CAR self-microemulsifying drug-delivery systems (SMEDDSs) were established, and the effects of different lipid materials on the absorption and metabolism of S-CAR were investigated. METHODS: Six kinds of lipid materials with different chemical structures including oleic acid, glycerol monooleate, glycerol trioleate, oleoyl macrogol-6 glycerides, soybean lecithin, and α-tocopherol were selected to be the oil phase. The S-CAR SMEDDSs were prepared by the same ratio. In vitro characteristics, in vitro release, in situ intestine absorption, and bile excretion, as well as the in vivo characteristic of relative bioavailability, were determined. KEY FINDINGS: The lipid structure significantly affected physical characteristics, the absorption and excretion rates of S-CAR SMEDDSs. The findings of rat-intestine perfusion experiments showed that the S-CAR SMEDDSs decreased the bile-excretion rate of S-CAR. Compared with the S-CAR group, the oleic acid and soybean lecithin groups decreased the bile excretion to 32% and 45%, respectively. Pharmacokinetic studies showed that the AUCs of these two groups were about 1.9 and 1.7 times more than that of the S-CAR group, and the mean retention time was extended. CONCLUSION: The SMEDDS using ionic lipids (oleic acid or soybean lecithin) as oil phase can increase the oral bioavailability of S-CAR by increasing the solubility and reducing the first-pass effect.

Role of Glucose Transporters in Drug Membrane Transport.

BACKGROUND: Glucose is the main energy component of cellular activities. However, as a polar molecule, glucose cannot freely pass through the phospholipid bilayer structure of the cell membrane. Thus, glucose must rely on specific transporters in the membrane. Drugs with a similar chemical structure to glucose may also be transported through this pathway. METHODS: This review describes the structure, distribution, action mechanism and influencing factors of glucose transporters and introduces the natural drugs mediated by these transporters and drug design strategies on the basis of this pathway. RESULTS: The glucose transporters involved in glucose transport are of two major types, namely, Na+-dependent and Na+-independent transporters. Glucose transporters can help some glycoside drugs cross the biological membrane. The transmembrane potential is influenced by the chemical structure of drugs. Glucose can be used to modify drugs and improve their ability to cross biological barriers. CONCLUSION: The membrane transport mechanism of some glycoside drugs may be related to glucose transporters. Glucose modification may improve the oral bioavailability of drugs or achieve targeted drug delivery.

Asymmetric Pseudocapacitors Based on Interfacial Engineering of Vanadium Nitride Hybrids.

Vanadium nitride (VN) shows promising electrochemical properties as an energy storage devices electrode, specifically in supercapacitors. However, the pseudocapacitive charge storage in aqueous electrolytes shows mediocre performance. Herein, we judiciously demonstrate an impressive pseudocapacitor performance by hybridizing VN nanowires with pseudocapacitive 2D-layered MoS2 nanosheets. Arising from the interfacial engineering and pseudocapacitive synergistic effect between the VN and MoS2, the areal capacitance of VN/MoS2 hybrid reaches 3187.30 mF cm-2, which is sevenfold higher than the pristine VN (447.28 mF cm-2) at a current density of 2.0 mA cm-2. In addition, an asymmetric pseudocapacitor assembled based on VN/MoS2 anode and TiN coated with MnO2 (TiN/MnO2) cathode achieves a remarkable volumetric capacitance of 4.52 F cm-3 and energy density of 2.24 mWh cm-3 at a current density of 6.0 mA cm-2. This work opens a new opportunity for the development of high-performance electrodes in unfavorable electrolytes towards designing high areal-capacitance electrode materials for supercapacitors and beyond.

Unraveling Reaction Mechanisms of Mo2C as Cathode Catalyst in a Li-CO2 Battery.

First-principles density functional theory calculations are first used to study possible reaction mechanisms of molybdenum carbide (Mo2C) as cathode catalysts in Li-CO2 batteries. By systematically investigating the Gibbs free energy changes of different intermediates during lithium oxalate (Li2C2O4) and lithium carbonate (Li2CO3) nucleations, it is theoretically demonstrated that Li2C2O4 could be stabilized as the final discharge product, preventing the further formation of Li2CO3. The surface charge distributions of Li2C2O4 adsorbing onto catalytic surfaces are studied by using Bader charge analysis, given that electron transfers are found between Li2C2O4 and Mo2C surfaces. The catalytic activities of catalysts are intensively evaluated toward the discharge and charge processes by calculating the electrochemical free energy diagrams to identify the overpotentials. Our studies promote the understanding of electrochemical processes and shed more light on the design and optimization of cathode catalysts for Li-CO2 batteries.

A Quasi-Solid-State Flexible Fiber-Shaped Li-CO2 Battery with Low Overpotential and High Energy Efficiency.

The rapid development of wearable electronics requires a revolution of power accessories regarding flexibility and energy density. The Li-CO2 battery was recently proposed as a novel and promising candidate for next-generation energy-storage systems. However, the current Li-CO2 batteries usually suffer from the difficulties of poor stability, low energy efficiency, and leakage of liquid electrolyte, and few flexible Li-CO2 batteries for wearable electronics have been reported so far. Herein, a quasi-solid-state flexible fiber-shaped Li-CO2 battery with low overpotential and high energy efficiency, by employing ultrafine Mo2 C nanoparticles anchored on a carbon nanotube (CNT) cloth freestanding hybrid film as the cathode, is demonstrated. Due to the synergistic effects of the CNT substrate and Mo2 C catalyst, it achieves a low charge potential below 3.4 V, a high energy efficiency of ≈80%, and can be reversibly discharged and charged for 40 cycles. Experimental results and theoretical simulation show that the intermediate discharge product Li2 C2 O4 stabilized by Mo2 C via coordinative electrons transfer should be responsible for the reduction of overpotential. The as-fabricated quasi-solid-state flexible fiber-shaped Li-CO2 battery can also keep working normally even under various deformation conditions, giving it great potential of becoming an advanced energy accessory for wearable electronics.

Phase interfaces within different vesicle shapes.

Liquid droplets on flat surfaces generally exhibit a contact angle in a range from 0 to [Formula: see text], but the two-phase interface within a vesicle membrane is very fascinating due to the involved force balance along three bending interfaces. Giant lipid vesicles encapsulated with the poly(ethylene glycol)/dextran aqueous two-phase system are established recently, and the phase interfaces within vesicle membrane are very interesting as experimentally observed. The developed theoretical framework by a combination of the Helfrich curvature elastic theory for vesicle membranes and self-consistent field theory for polymers has been extended to explore aqueous two phases within vesicles. The intrinsic contact angle [Formula: see text] that represents the material parameter, is introduced to describe this phase interfaces within vesicles, especially the transitions from complete wetting to partial wetting, from partial wetting to complete dewetting. The dependence of intrinsic contact angles on the parameters, such as the interaction strengths between the polymers [Formula: see text] and between the membrane and polymer [Formula: see text], the volume fraction [Formula: see text], impermeability of the membrane to the enclosed polymers [Formula: see text] and membrane spontaneous curvature c 0, are thoroughly investigated, as well as these wetting/dewetting transitions are extensively discussed in the present study.

Exploration of cell division times during bacterial cytokinesis.

Filamenting temperature-sensitive mutant Z (FtsZ), an essential cell division protein in bacteria, has recently emerged as an important and exploitable antibacterial target. The perturbation of FtsZ assembly is found to have an effect on cell cytokinesis and cell survival. Cell division time is an important physical parameter in cell cytokinesis. Here, the theoretical framework that has been developed by combining a phase field model for rod-shaped cells with a kinetic description for FtsZ ring maintenance is extended to explore cell division times during bacterial cytokinesis. The cell division times of around 72 s in the numerical studies have the same magnitude as the division time of several minutes observed physiologically. The dependence of the cell division time on parameters such as the initial state of rod-shaped cells and various kinetic rates of FtsZ assembly dynamics is thoroughly investigated. The theoretical analysis of the relations between the cell division time and these parameters is found to coincide well with the numerical calculated results.

Hierarchically ordered mesoporous carbon/graphene composites as supercapacitor electrode materials.

Hierarchically ordered mesoporous carbon/graphene (OMC/G) composites have been fabricated by means of a solvent-evaporation-induced self-assembly (EISA) method. The structures of these composites are characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and nitrogen adsorption-desorption at 77 K. These results indicate that OMC/G composites possess the hierarchically ordered hexagonal p6mm mesostructure with the lattice unit parameter and pore diameter close to 10 nm and 3 nm, respectively. The specific surface area of OMC/G composites after KOH activation is high up to 2109.2 m(2) g(-1), which is significantly greater than OMC after activation (1474.6 m(2) g(-1)). Subsequently, the resulting OMC/G composites as supercapacitor electrode materials exhibit an outstanding capacitance as high as 329.5 F g(-1) in 6 M KOH electrolyte at a current density of 0.5 A g(-1), which is much higher than both OMC (234.2 F g(-1)) and a sample made by mechanical mixing of OMC with graphene (217.7 F g(-1)). In addition, the obtained OMC/G composites display good cyclic stability, and the final capacitance retention is approximately 96% after 5000 cycles. These ordered mesopores in the OMC/G composites are beneficial to the accessibility and rapid diffusion of the electrolyte, while graphene in OMC/G composites can also facilitate the transport of electrons during the processes of charging and discharging owing to its high conductivity, thereby leading to an excellent energy storage performance. The method demonstrated in this work would open up a new route to design and develop graphene-based architectures for supercapacitor applications.

Effects of various kinetic rates of FtsZ filaments on bacterial cytokinesis.

Cell morphodynamics during bacterial cytokinesis are theoretically explored by a combination of phase field model for rod-shaped cells and a kinetic description for FtsZ ring maintenance. The division times and cell shapes have been generally decided by the competition between the constriction forces generated by FtsZ rings and the curvature elastic energy for cells. The dependences of cell morphodynamics during bacterial cytokinesis on various kinetic rates of FtsZ filaments are focused in the present study. It is found that the obtained results with the experimental parameters are well comparable to the observed results physiologically. Likewise, the quasi-steady states for FtsZ rings are found to be well consistent with the theoretical results derived from the kinetic description of FtsZ rings. In addition, morphological phase diagram is presented as functions of the membrane associate rate for both short FtsZ filaments and free FtsZ monomers, and the depolymerization rate of GDP-bound FtsZ monomers at the tip of filaments within the ring. Our results would provide a better understanding of the details of in vivo kinetics, including the kinetic rates within FtsZ rings.

Wetting transitions within membrane compartments.

A biomimetic membrane in contact with several aqueous phases is theoretically studied using a combination of Helfrich curvature elasticity theory for fluid membranes and self-consistent field theory for polymers in solutions. Two phases that are thermodynamically formed by phase separation of aqueous solutions, as well as stable and metastable shapes of fluid vesicles, have been observed. The wetting transitions from complete to partial wetting and to complete dewetting are identified within a membrane compartment. The dependences of wetting transitions on material parameters, such as the intrinsic contact angles θin, the interaction strengths between the polymers χαß and between the membrane and the polymer ηp, and impermeability of the membrane to the enclosed polymers ζp, are investigated. For a given χαß, impermeability ζp and affinity to the membrane ηp, θin is found to be a constant and independent of the reduced volume of vesicles and the volume fraction of two phases.

Shapes of vesicles encapsulating two aqueous phases.

Motivated by recent experiments, vesicles encapsulating two aqueous phases are theoretically explored using a combination of Helfrich curvature elasticity theory for fluid membranes and self-consistent field theory for polymers. The spatial distributions of two polymers, α and ß, have been obtained, and two thermodynamic phases occur, as expected. Stable or metastable shapes of fluid and closed vesicles have also been achieved. Due to the impenetrability of the membrane to polymer, the available spaces of polymers α and ß are limited and the conformational entropies for the polymers are reduced. Different chain segments that possess different permeability to the membrane would induce different inhomogeneous entropic pressures on the membrane, thereby leading to shape transformations of the vesicles. In the present study, the typical shapes of vesicles encapsulating two phases are studied as functions of the concentrations of polymers α and ß, and the interactions between the chain segments and the membrane. The two phases formed by polymers α and ß are also found to be altered and have been discussed in detail. In addition, morphological phase diagrams are presented as a function of the reduced volume, v. The phase boundaries between oblates and prolates, and oblates and stomatocytes of vesicles encapsulating two phases are found to move toward the higher reduced volume, and oblates occupy a much wider range of the reduced volume compared with 'neat' vesicles.

Polymerization of actin filaments coupled with adenosine triphosphate hydrolysis: Brownian dynamics and theoretical analysis.

Polymerization dynamics of single actin filaments coupled with adenosine triphosphate (ATP) hydrolysis is investigated via both theoretical analysis and Brownian dynamics simulations. Brownian dynamics simulations have been applied recently to study the growth behaviors of long filaments as a function of the free actin monomer concentrations, C(T), which is found to be in agreement with the associated experiments. In the present study, both ATP cap length and length diffusivity are studied as a function of the free ATP-actin monomer concentrations, C(T). The exact analytical expressions are found to be in perfect consistency with Brownian dynamics simulations. Likewise, we find that the length diffusion coefficient is peaked near the critical concentration, C(T,cr). It is, therefore, expected that the dependence of length diffusivity on ATP-actin monomer concentrations is utilized to analyze the surprising experiments on the length fluctuations of individual actin filaments.