Endoplasmic-reticulum-like catalyst coating on separator to enhance polysulfides conversion for lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries with high theoretical specific energy of 2600 Wh kg^(-1) are one of promising candidates for next-generation energy storage devices.However,the severe shuttle effect of intermediate polysulfides leads to rapid capacity decay during battery cycling,especially at high sulfur loading and high current density.Herein,the MnO nanoparticles covered carbon with endoplasmic-reticulum-like structure(MnO@ERC)as separator coating for Li-S batteries is proposed.The MnO@ERC coating can act as upper current collector to enhance electrical conductivity of cathode and decrease the interface impedance of the whole battery.More importantly,both the polar MnO nanoparticles and Mn_(3)O_(4) formed at the end of the charging process can catalyze the conversion of lithium polysulfides,which is convinced by the high adsorption energy and the elongate S–S bond.As a result,Li-S batteries based on MnO@ERC coating separator showed stable cycle for 350 cycles under 0.5C,high discharge specific capacity of 783.6m Ah g^(-1) after 100 cycles at 0.2 C,534.7 m Ah g^(-1) after 100 cycles under the sulfur loading of 5.26 mg cm;and low self-discharge rate of 9.1%after resting 48 h..

To gel or not to gel：A prior prediction of gelation in solvent mixtures

The gelation behaviours of low molecular weight gelators 1,3：2,5：4.6-tris（3,4-dichlorobenzylidene）-Dmannitol（G1） and 2,4-（3.4-dichlorobenzylidene）-N-（3-aminopropyl）-D-gluconamide（G2） in 34 solvents have been studied.We found that sample dissolved at low concentrations may become a gel or precipitate at higher concentrations.The Hansen solubility parameters（HSPs） and a Teas plot were employed to correlate the gelation behaviours with solvent properties,but with no success if the concentration of the tests was not maintained constant.Instead,on the basis of the gelation results obtained for the G1 and G2 in single solvents,we studied the gelation behaviours of G1 and G2 in23 solvent mixtures and found that the tendency of a gelator to form a gel in mixed solvents is strongly correlated with its gelation behaviours in good solvents.If the gelation occurs in a good solvent at higher concentrations,it will take place as well in a mixed solvent（the good solvent plus a poor solvent） at a certain volume ratio.In contrast,if the gelator forms a precipitate in a good solvent at higher concentrations,no gelation is to be observed in the mixed solvents.A gelation rule for mixed solvents is thus proposed,which may facilitate decision making with regard to solvent selection for gel formation in the solvent mixtures in practical applications.

The gelation rule of the polyol acetal derivatives in binary solvent mixtures

The gelation properties of polyol acetal derivatives including 2,4-（3,4-dichlorobenzylidene）-D-sorbitol（DCBS）, 1,3：2,4-di（3,4-dichlorobenzylidene）-D-sorbitol（DDCBS） and 1,3：2,5：4,6-tris（3,4-dichlorobenzylidene）-D-mannitol（TDCBM） in 35 single solvents and 39 binary solvent mixtures have been studied. FTIR and XRD results suggest that the self-assembly patterns of the gelator will not change in either the single solvent component or the corresponding solvent mixtures, but the critical gelation concentration（CGC）will be influenced. The results of SEM and rheology showed that the formation of true gels at saturated concentrations. Improving the heating temperature may promote the dissolving of gelators which are even insoluble at the temperature of the solvent boiling point and change the gelation behaviors. FloryHuggins parameter（x） was used to predict the gelation behavior of DCBS in the mixed solvents, and it is shown that the x values for the mixed solvents that can be gelled by DCBS are either greater or smaller than those for the selected good solvents.