Advances in metal-organic framework coatings: versatile synthesis and broad applications.

Metal-organic frameworks (MOFs) as a new kind of porous crystalline materials have attracted much interest in many applications due to their high porosity, diverse structures, and controllable chemical structures. However, the specific geometrical morphologies, limited functions and unsatisfactory performances of pure MOFs hinder their further applications. In recent years, an efficient approach to synthesize new composites to overcome the above issues has been achieved, by integrating MOF coatings with other functional materials, which have synergistic advantages in many potential applications, including batteries, supercapacitors, catalysis, gas storage and separation, sensors, drug delivery/cytoprotection and so on. Nevertheless, the systemic synthesis strategies and the relationships between their structures and application performances have not been reviewed comprehensively yet. This review emphasizes the recent advances in versatile synthesis strategies and broad applications of MOF coatings. A comprehensive discussion of the fundamental chemistry, classifications and functions of MOF coatings is provided first. Next, by modulating the different states (e.g. solid, liquid, and gas) of metal ion sources and organic ligands, the synthesis methods for MOF coatings on functional materials are systematically summarized. Then, many potential applications of MOF coatings are highlighted and their structure-property correlations are discussed. Finally, the opportunities and challenges for the future research of MOF coatings are proposed. This review on the deep understanding of MOF coatings will bring better directions into the rational design of high-performance MOF-based materials and open up new opportunities for MOF applications.

Elastic and Li-ion-percolating hybrid membrane stabilizes Li metal plating.

Lithium metal batteries are capable of revolutionizing the battery marketplace for electrical vehicles, owing to the high capacity and low voltage offered by Li metal. Current exploitation of Li metal electrodes, however, is plagued by their exhaustive parasitic reactions with liquid electrolytes and dendritic growth, which pose concerns to both cell performance and safety. We demonstrate that a hybrid membrane, both elastic and Li+-ion percolating, can stabilize Li plating/stripping with high Coulombic efficiency. The compact packing of a Li+ solid electrolyte phase offers percolated Li+-conducting channels and the consequent infiltration of an elastic polymer endows membrane flexibility to accommodate volume changes. The protected electrode allows Li plating with 95.8% efficiency for 200 cycles and stable operation of an LTO|Li cell for 2,000 cycles. This rationally structured membrane represents an interface engineering approach toward stabilized Li metal electrodes.

Stabilizing Lithium Plating by a Biphasic Surface Layer Formed In†Situ.

The dendritic growth of Li metal leads to electrode degradation and safety concerns, impeding its application in building high energy density batteries. Forming a protective layer on the Li surface that is electron-insulating, ion-conducting, and maintains an intimate interface is critical. We herein demonstrate that Li plating is stabilized by a biphasic surface layer composed of a lithium-indium alloy and a lithium halide, formed in situ by the reaction of an electrolyte additive with Li metal. This stabilization is attributed to the fast lithium migration though the alloy bulk and lithium halide surface, which is enabled by the electric field across the layer that is established owing to the electron-insulating halide phase. A greatly stabilized Li-electrolyte interface and dendrite-free plating over 400 hours in Li|Li symmetric cells using an alkyl carbonate electrolyte is demonstrated. High energy efficiency operation of the Li4 Ti5 O12 (LTO)|Li cell over 1000 cycles is achieved.

Directing the Lithium-Sulfur Reaction Pathway via Sparingly Solvating Electrolytes for High Energy Density Batteries.

The lithium-sulfur battery has long been seen as a potential next generation battery chemistry for electric vehicles owing to the high theoretical specific energy and low cost of sulfur. However, even state-of-the-art lithium-sulfur batteries suffer from short lifetimes due to the migration of highly soluble polysulfide intermediates and exhibit less than desired energy density due to the required excess electrolyte. The use of sparingly solvating electrolytes in lithium-sulfur batteries is a promising approach to decouple electrolyte quantity from reaction mechanism, thus creating a pathway toward high energy density that deviates from the current catholyte approach. Herein, we demonstrate that sparingly solvating electrolytes based on compact, polar molecules with a 2:1 ratio of a functional group to lithium salt can fundamentally redirect the lithium-sulfur reaction pathway by inhibiting the traditional mechanism that is based on fully solvated intermediates. In contrast to the standard catholyte sulfur electrochemistry, sparingly solvating electrolytes promote intermediate- and short-chain polysulfide formation during the first third of discharge, before disproportionation results in crystalline lithium sulfide and a restricted fraction of soluble polysulfides which are further reduced during the remaining discharge. Moreover, operation at intermediate temperatures ca. 50 °C allows for minimal overpotentials and high utilization of sulfur at practical rates. This discovery opens the door to a new wave of scientific inquiry based on modifying the electrolyte local structure to tune and control the reaction pathway of many precipitation-dissolution chemistries, lithium-sulfur and beyond.

Inhibiting Polysulfide Shuttle in Lithium-Sulfur Batteries through Low-Ion-Pairing Salts and a Triflamide Solvent.

The step-change in gravimetric energy density needed for electrochemical energy storage devices to power unmanned autonomous vehicles, electric vehicles, and enable low-cost clean grid storage is unlikely to be provided by conventional lithium ion batteries. Lithium-sulfur batteries comprising lightweight elements provide a promising alternative, but the associated polysulfide shuttle in typical ether-based electrolytes generates loss in capacity and low coulombic efficiency. The first new electrolyte based on a unique combination of a relatively hydrophobic sulfonamide solvent and a low ion-pairing salt, which inhibits the polysulfide shuttle, is presented. This system behaves as a sparingly solvating electrolyte at slightly elevated temperatures, where it sustains reversible capacities as high as 1200-1500 mAh g-1 over a wide range of current density (2C-C/5, respectively) when paired with a lithium metal anode, with a coulombic efficiency of >99.7 % in the absence of LiNO3 additive.

Interwoven MXene Nanosheet/Carbon-Nanotube Composites as Li-S Cathode Hosts.

The complex surface chemistry that dictates the interaction between MXene and polysulfides - the formation of thiosulfate via consumption of -OH surface groups, followed by Lewis acid-base interaction between the exposed Ti atoms and polysulfides - is unravelled. Interweaving carbon nanotubes between the MXene layers creates a porous, conductive network with high polysulfide adsorptivity, enabling sulfur hosts with excellent performance even at high loading (5.5 mg cm-2 ).

Long-Life and High-Areal-Capacity Li-S Batteries Enabled by a Light-Weight Polar Host with Intrinsic Polysulfide Adsorption.

Lithium-sulfur batteries are attractive electrochemical energy storage systems due to their high theoretical energy density and very high natural abundance of sulfur. However, practically, Li-S batteries suffer from short cycling life and low sulfur utilization, particularly in the case of high-sulfur-loaded cathodes. Here, we report on a light-weight nanoporous graphitic carbon nitride (high-surface-area g-C3N4) that enables a sulfur electrode with an ultralow long-term capacity fade rate of 0.04% per cycle over 1500 cycles at a practical C/2 rate. More importantly, it exhibits good high-sulfur-loading areal capacity (up to 3.5 mAh cm(-2)) with stable cell performance. We demonstrate the strong chemical interaction of g-C3N4 with polysulfides using a combination of spectroscopic experimental studies and first-principles calculations. The 53.5% concentration of accessible pyridinic nitrogen polysulfide adsorption sites is shown to be key for the greatly improved cycling performance compared to that of N-doped carbons.

A nitrogen and sulfur dual-doped carbon derived from polyrhodanine@cellulose for advanced lithium-sulfur batteries.

A sulfur electrode exhibiting strong polysulfide chemisorption using a porous N, S dual-doped carbon is reported. The synergistic functionalization from the N and S heteroatoms dramatically modifies the electron density distribution and leads to much stronger polysulfide binding. X-ray photoelectron spectroscopy studies combined with ab initio calculations reveal strong Li(+) -N and Sn (2-) -S interactions. The sulfur electrodes exhibit an ultralow capacity fading of 0.052% per cycle over 1100 cycles.

A highly efficient polysulfide mediator for lithium-sulfur batteries.

The lithium-sulfur battery is receiving intense interest because its theoretical energy density exceeds that of lithium-ion batteries at much lower cost, but practical applications are still hindered by capacity decay caused by the polysulfide shuttle. Here we report a strategy to entrap polysulfides in the cathode that relies on a chemical process, whereby a host--manganese dioxide nanosheets serve as the prototype--reacts with initially formed lithium polysulfides to form surface-bound intermediates. These function as a redox shuttle to catenate and bind 'higher' polysulfides, and convert them on reduction to insoluble lithium sulfide via disproportionation. The sulfur/manganese dioxide nanosheet composite with 75 wt% sulfur exhibits a reversible capacity of 1,300 mA h g(-1) at moderate rates and a fade rate over 2,000 cycles of 0.036%/cycle, among the best reported to date. We furthermore show that this mechanism extends to graphene oxide and suggest it can be employed more widely.

Surface-enhanced redox chemistry of polysulphides on a metallic and polar host for lithium-sulphur batteries.

The lithium-sulphur battery relies on the reversible conversion between sulphur and Li2S and is highly appealing for energy storage owing to its low cost and high energy density. Porous carbons are typically used as sulfur hosts, but they do not adsorb the hydrophilic polysulphide intermediates or adhere well to Li2S, resulting in pronounced capacity fading. Here we report a different strategy based on an inherently polar, high surface area metallic oxide cathode host and show that it mitigates polysulphide dissolution by forming an excellent interface with Li2S. Complementary physical and electrochemical probes demonstrate strong polysulphide/Li2S binding with this 'sulphiphilic' host and provide experimental evidence for surface-mediated redox chemistry. In a lithium-sulphur cell, Ti4O7/S cathodes provide a discharge capacity of 1,070 mAh g(-1) at intermediate rates and a doubling in capacity retention with respect to a typical conductive carbon electrode, at practical sulphur mass fractions up to 70 wt%. Stable cycling performance is demonstrated at high rates over 500 cycles.

[Experience of the surgical comprehensive treatment on severe acute pancreatitis].

OBJECTIVE: To summary the experience of the surgical comprehensive treatment of severe acute pancreatitis (SAP). METHODS: From July 1999 to December 2009, a total of 506 patients suffered SAP were admitted with a mean APACHE II score 12.8 ± 4.6. There were 270 male and 236 female, aged from 16 to 89 years, mean age 43 years. SAP patients were treated by the SAP treatment team which consisted of pancreatic specialized and multidisciplinary doctors. Two hundreds and thirty-four cases (46.2%) received non-operative treatment and 272 cases (53.8%) received surgical intervention. RESULTS: In 506 cases, 445 patients were cured and 52 patients died (31 died in early stage, 21 died in later stage), 9 cases discharged automatically. The overall incidence of complication, overall mortality and overall curative rate were 29.4% (149/506), 10.3% (52/506) and 87.9% (445/506), respectively. The incidences of complication in non-operative group and in surgical intervention group were 27.8% (65/234) and 30.9% (84/272), respectively (P > 0.05). The mortality in non-operative group and in surgical intervention group were 9.4% (22/234) and 11.0% (30/272), respectively (P > 0.05). The curative rates in non-operative group and in surgical intervention group were 90.6% (212/234) and 85.7% (233/272), respectively (P > 0.05). CONCLUSIONS: Patients should be treated in ICU in the early phase of the disease when APACHE II score > 10. Pancreatic specialized and multidisciplinary team treatment, appropriate choice of timing, indication and procedure of surgical intervention and details of drainage are vital to the prognosis of SAP.

Experience of the surgical comprehensive treatment on severe acute pancreatitis / 中华外科杂志

<p><b>OBJECTIVE</b>To summary the experience of the surgical comprehensive treatment of severe acute pancreatitis (SAP).</p><p><b>METHODS</b>From July 1999 to December 2009, a total of 506 patients suffered SAP were admitted with a mean APACHE II score 12.8 ± 4.6. There were 270 male and 236 female, aged from 16 to 89 years, mean age 43 years. SAP patients were treated by the SAP treatment team which consisted of pancreatic specialized and multidisciplinary doctors. Two hundreds and thirty-four cases (46.2%) received non-operative treatment and 272 cases (53.8%) received surgical intervention.</p><p><b>RESULTS</b>In 506 cases, 445 patients were cured and 52 patients died (31 died in early stage, 21 died in later stage), 9 cases discharged automatically. The overall incidence of complication, overall mortality and overall curative rate were 29.4% (149/506), 10.3% (52/506) and 87.9% (445/506), respectively. The incidences of complication in non-operative group and in surgical intervention group were 27.8% (65/234) and 30.9% (84/272), respectively (P > 0.05). The mortality in non-operative group and in surgical intervention group were 9.4% (22/234) and 11.0% (30/272), respectively (P > 0.05). The curative rates in non-operative group and in surgical intervention group were 90.6% (212/234) and 85.7% (233/272), respectively (P > 0.05).</p><p><b>CONCLUSIONS</b>Patients should be treated in ICU in the early phase of the disease when APACHE II score > 10. Pancreatic specialized and multidisciplinary team treatment, appropriate choice of timing, indication and procedure of surgical intervention and details of drainage are vital to the prognosis of SAP.</p>

[A study of sleep stage classification based on permutation entropy for electroencephalogram].

This paper presents a new method for automatic sleep stage classification which is based on the EEG permutation entropy. The EEG permutation entropy has notable distinction in each stage of sleep and manifests the trend of regular transforming. So it can be used as features of sleep EEG in each stage. Nearest neighbor is employed as the pattern recognition method to classify the stages of sleep. Experiments are conducted on 750 sleep EEG samples and the mean identification rate can be up to 79.6%.