Interconnected NiCo2O4 nanosheet arrays grown on carbon cloth as a host, adsorber and catalyst for sulfur species enabling high-performance Li-S batteries.

Li-S batteries are a promising next-generation electrochemical energy-storage system due to their high energy density, as well as the abundance and low cost of sulfur. However, the low conductivity of sulfur and Li2S/Li2S2, as well as the dissolution and shuttling of intermediate lithium polysulfides, is a great challenge for high-performance Li-S batteries. Herein, interconnected NiCo2O4 nanosheet arrays grown on carbon cloth (CC) are applied as the cathode (S/NiCo2O4/CC) in Li-S batteries for accommodating sulfur. The obtained cathode shows high conductivity, high dispersion of sulfur species and excellent polysulfide adsorption and catalytic properties. As a result, significantly higher specific capacity (1480 vs. 1048 mA h g-1 at 0.1C) and greatly enhanced rate performance (624 vs. 215 mA h g-1 at 2C) are obtained for the S/NiCo2O4/CC cathode in comparison to S/CC. Further, the S/NiCo2O4/CC cathode demonstrates a low capacity decay of 0.060% per cycle over 400 cycles at 0.5C.

Small things make a big difference: binder effects on the performance of Li and Na batteries.

Li and Na batteries are very important as energy storage devices for electric vehicles and smart grids. It is well known that, when an electrode is analysed in detail, each of the components (the active material, the conductive carbon, the current collector and the binder) makes a portion of contribution to the battery performance in terms of specific capacity, rate capability, cycle life, etc. However, there has not yet been a review on the binder, though there are already many review papers on the active materials. Binders make up only a small part of the electrode composition, but in some cases, they play an important role in affecting the cycling stability and rate capability for Li-ion and Na-ion batteries. Poly(vinylidene difluoride) (PVDF) has been the mainstream binder, but there have been discoveries that aqueous binders can sometimes make a battery perform better, not to mention they are cheaper, greener, and easier to use for electrode fabrication. In this review, we focus on several kinds of promising electrode materials, to show how their battery performance can be affected significantly by binder materials: anode materials such as Si, Sn and transitional metal oxides; cathode materials such as LiFePO4, LiNi1/3Co1/3Mn1/3O2, LiCoO2 and sulphur.

Promoted hydrogen release from ammonia borane with mannitol via a solid-state reaction route.

Promoted hydrogen release from ammonia borane (NH(3)BH(3), AB) with mannitol (C(6)H(8)(OH)(6), MA) additive is reported. It is found that for the MA/2AB sample, the dehydrogenation temperature is lowered by ~25 °C compared to that of neat AB, the liberation of undesired byproduct borazine is suppressed, and the released ammonia can be removed by using anhydrous MgCl(2) as absorber. The analyses of Raman, Fourier transform infrared spectroscopy and (11)B nuclear magnetic resonance spectroscopy demonstrate the breaking of B-N, B-H and O-H bonds and the formation of B-O bonds for the dehydrogenation process of MA/2AB. These results suggest a solid-state dehydrogenation reaction between AB and MA: the B-H(δ-) bonds in AB and the O-H(δ+) bonds in MA combine with each other to release H(2). Furthermore, the use of the perfect -OH carrier MA as additive leads to a straightforward understanding of the improved dehydrogenation of AB under the effect of hydroxyl groups in the solid state.

Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts.

Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal-air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M(x)Mn(3-x)O(4) (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M(x)Mn(3-x)O(4) from the reduction of amorphous MnO(2) in aqueous M(2+) solution. The prepared Co(x)Mn(3-x)O(4) nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co-Mn-O spinels are also interpreted by experiment and first-principle theoretical studies.