Smaller sulfur molecules promise better lithium-sulfur batteries.

The lithium-sulfur battery holds a high theoretical energy density, 4-5 times that of today's lithium-ion batteries, yet its applications have been hindered by poor electronic conductivity of the sulfur cathode and, most importantly, the rapid fading of its capacity due to the formation of soluble polysulfide intermediates (Li(2)S(n), n = 4-8). Despite numerous efforts concerning this issue, combatting sulfur loss remains one of the greatest challenges. Here we show that this problem can be effectively diminished by controlling the sulfur as smaller allotropes. Metastable small sulfur molecules of S(2-4) were synthesized in the confined space of a conductive microporous carbon matrix. The confined S(2-4) as a new cathode material can totally avoid the unfavorable transition between the commonly used large S(8) and S(4)(2-). Li-S batteries based on this concept exhibit unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior rate capability, which promise a practicable battery with high energy density for applications in portable electronics, electric vehicles, and large-scale energy storage systems.

[Study on microwave-templated synthesis mechanism of LiMn2O4 by infrared spectroscopy].

In this paper, LiMn2O4 was synthesized by the microwave-template method, and the synthesis mechanism was studied by the in-situ FTIR. It was confirmed by the FTIR that polyacrylamide was decomposed gradually during the spinel LiMn2O4 preparation, and there was some chemical bond between the reactants and polyacrylamide in the precursors. Polyacrylamide acted as template in the course of the preparation of precursors and forming of spinel lithium manganese oxide compound. As a result of the certain chemical bond, the controlling and adjusting of the LiMn2O4 crystalline were realized, so that agglomeration and lacunae framework of the spinel was adjusted.