Insight into the probability of ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as the functional electrolyte additive in lithium-sulfur batteries.

Enhancing the flame retardancy of electrolytes and the stability of lithium anodes is of great significance to improve the safety performance of lithium-sulfur (Li-S) batteries. It is well known that the most commonly used ether based electrolyte solvents in Li-S batteries have a lower flash point and higher volatility than the ester electrolyte solvents in Li-ion batteries. Hence, lithium-sulfur batteries have greater safety risks than lithium-ion batteries. Herein, ethoxy(pentafluoro)cyclotriphosphazene (PFPN), which is commonly used as a flame retardant for ester electrolytes in lithium-ion batteries, is utilized as both a film-forming electrolyte additive and a flame retardant additive for the ether electrolyte to investigated its applicability in Li-S batteries. It is found that the ether electrolyte containing PFPN not only has good flame retardant properties and a wide potential window of about 5 V, but also can form a stable SEI film on the surface of a lithium anode. As a result, with the ether-based electrolyte containing 10 wt% PFPN, Li-Cu and Li-S batteries all delivered a stable cycling performance with a high coulombic Efficiency and a long-lifespan performance, which were all superior to the batteries using the ether-based electrolyte without PFPN. This study demonstrates an effective solution to solve the problems of flammable ether-based electrolytes and reactive lithium anodes, and it may contribute to the development of safe Li-S batteries.

Research status of polysiloxane-based piezoresistive flexible human electronic sensors.

Flexible human body electronic sensor is a multifunctional electronic device with flexibility, extensibility, and responsiveness. Piezoresistive flexible human body electronic sensor has attracted the extensive attention of researchers because of its simple preparation process, high detection sensitivity, wide detection range, and low power consumption. However, the wearability and affinity to the human body of traditional flexible human electronic sensors are poor, while polysiloxane materials can be mixed with other electronic materials and have good affinity toward the human body. Therefore, polysiloxane materials have become the first choice of flexible matrixes. In this study, the research progress and preparation methods of piezoresistive flexible human electronic sensors based on polysiloxane materials in recent years are summarized, the challenges faced in the development of piezoresistive flexible human electronic sensors are analyzed, and the future research directions are prospected.

Fast polysulfide catalytic conversion and self-repairing ability for high loading lithium-sulfur batteries using a permselective coating layer modified separator.

Li-S batteries are considered as one of the most promising battery systems because of their large theoretical capacity and high energy density. However, the "shuttle effect" of soluble polysulfides and sluggish electrochemical redox kinetics of Li-S batteries could cause a broken electrode structure and poor electrochemical performance. Herein, a high-performance and stable Li-S battery has been demonstrated by employing organo-polysulfide chain modified acetylene black (ABPS) as the coating layer on the separator. In addition to the traditional advantages of fast electron transport and polysulfide-interception ability of the carbon coating layer, the grafted organo-polysulfide chain endows the ABPS coating layer with permselectivity for lithium ion against polysulfides, electrocatalytic ability for the sluggish redox kinetics and self-repairing ability for the broken electrode. Hence, the battery prepared using an ABPS-coated separator delivers the best cycling performance (970 mA h g-1 at 0.2 C after 100 cycles) and rate performance (805 mA h g-1 at 2 C) as compared to the cells using acetylene black (AB)-coated or Celgard separators. Moreover, the Li-S battery prepared using an ABPS-coated separator exhibits a stable cycling performance at 1 C over 500 cycles with a low degradation of 0.04% per cycle, and a high coulombic efficiency (near 100%). Furthermore, as the sulfur loading was increased to 6.8 mg cm-2, the Li-S battery using the ABPS-coated separator still could deliver a high areal capacity of 6.03 mA h cm-2 with a low electrolyte/sulfur ratio (E/S = 4, µLelectrolyte mgS-1) after 170 cycles. Significantly, ABPS is an effective coating layer material for improving and stabilizing Li-S batteries.

Multidimensional Polycation ß-Cyclodextrin Polymer as an Effective Aqueous Binder for High Sulfur Loading Cathode in Lithium-Sulfur Batteries.

Although the lithium-sulfur battery has attracted significant attention because of its high theoretical energy density and low cost of elemental sulfur, its real application is still hindered by multiple challenges, especially the polysulfides shuttled between the cathode and anode electrodes. By originating from ß-cyclodextrin and introducing a quaternary ammonium cation into ß-cyclodextrin polymer, a new multifunctional aqueous polycation binder (ß-CDp-N(+)) for the sulfur cathode is obtained. The unique hyperbranched network structure of the new binder ß-CDp-N(+) as well as its multidimensional noncovalent interactions and the introduced cations endowed ß-CDp-N(+) with some new abilities: a sulfur-electrode-stabilized ability, a polysulfides-immobilized ability, and a volume-accommodated ability, which help to ease the primary problems of the lithium-sulfur battery, i.e., the shuttle of polysulfides and the volume change of the sulfur during charge and discharge. It is demonstrated that cycling performance and rate capability of the cathodes can be the improved by using ß-CDp-N(+) as the binder compared to other well-known binders. Even with high sulfur loading of 5.5 mg cm(-2), the cathode with ß-CDp-N(+) still can deliver an areal capacity of 4.4 mAh cm(-2) at 50 mA g(-1) after 45 cycles, which is much higher than that achieved using the cathode with the conventional binder (0.9 mAh cm(-2)).

1,4,10,13-Tetra-oxa-7,16-diazo-nia-cyclo-octa-decane bis-(1H-pyrrole-2-carboxyl-ate).

In the title salt, C12H28N2O4 (2+)·2C5H4NO2 (-), the 1,4,10,13-tetra-oxa-7,16-di-aza-cyclo-octa-decane dication possesses inversion symmetry. In the crystal, the pyrrole-carboxyl-ate anions are linked via pairs of N-H⋯O hydrogen bonds, forming inversion dimers. These dimers are linked by the dications, via N-H⋯O hydrogen bonds, forming chains propagating along [110].