Lithium carbon-sulfur composites

A catalyst that can prevent polysulfide anions from precipitating as solids would be highly desirable. While a catalyst still remains to be discovered, several approaches, common in catalysis, have been employed to improve the cycling performance of lithium-sulfur batteries. For example, new electrolytes [18-21], protective films [22], solubiHzed sulfides [23], and new cathodes [24] have been developed. However, the performance results have either not been reported or have been found to be inadequate for practical applications. For example, a disordered mesoporous carbon-sulfur composite in conjunction with ionic liquid electrolytes has been fabricated. This system achieves high initial capacity that deteriorates rapidly [20]. 

N. Jayaprakash, J. Shen, S.S. Moganty, A. Corona and L.A. Archer, Porous hollow carbon sulfur composites for high-power lithium-sulfur batteries, Angew. Chem. Int. Ed. 50, 2011,5904-5908. 

Like cements, the elemental composition is determined by XRF or AAS techniques. The XRF bead is made using lithium tetraborate at 1050°C. Sulfide content cannot be determined by XRF. Sulfite, SO3 , and sulfate, S04 , are safely analyzed by XRF. Na2C03 -I- K2CO3 fusion is carried out for Ca, Mg, Fe, and A1 analysis by AAS. Lanthanum chloride is used as a sulfate interference suppressant. Gravimetric sulfate determinations are also carried out by precipitation as barium sulfate. The Leco Carbon-Sulfur Analyzer can also be used for quality control purposes. The fluoride is determined by XRF or a pyrohydrolysis method. The measurement of particle size distribution is carried out in a manner similar to that for cements and clays. 

L. Yuan, H. Yuan, X. Qiu, L. Chen, W. Zhu, Improvement of cycle property of sulfur-coated multi-walled carbon nanotubes composite cathode for lithium/sulfur batteries , J. Power Sources, 189, 1141-1146, 2009. 

Concerning the composition of alkali polysulfide, the yield of thiolane 7 suffered none in utilizing alkali polysulfide prepared from hydrated sodium sulfide or lithium or potassium sulfide rather than anhydrous sodium sulfide. When the ratio of sulfur to hydrated sodium sulfide was 8 1 or greater, the thiolane 7 resulted whereas at a ratio of 4 1, or using commercial Na, several components containing both sulfur and carbon were detected in me solid proauct. 

Wang, J. Chew, S.Y. Zhao, Z.W. Ashraf, S. Wexler, D. Chen, J. Ng, S.H. Chou, S.L. Liu, H.K., Sulfur-mesoporous carbon composites in conjimction with a novel ionic Uquid electrolyte for lithium rechargeable batteries. Carbon, 2008,46, 229-235. 

A typical Li-S cell consists of a lithium metal anode and a sulfur-carbon composite cathode with an organic liquid electrolyte in between, which is shown in Fig. 1. The Li-S chemistry is based on the following conversion reaction ... 

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