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Poly(ethylene oxide)-coated sulfur/carbon (S/C/PEO) composite with a high sulfur loading is prepared to improve the performance of lithium-sulfur batteries. By magnetic string, 3.7 wt% PEO is coated onto the surface of ball-milling obtained S/C composite, leading to synthesis of S/C/PEO composite containing 78 wt% S. It is confirmed from a series of measurements that PEO covers the S/C composite uniformly, and PEO coating is quite effective in stabilizing the electrochemical performance. When employed as cathode for lithium-sulfur batteries, S/C/PEO delivers an initial discharge capacity of 989.6 mAh g and remains 648.3 mAh g after 110 cycles at a discharge/charge rate of 1 C (based on sulfur weight). Meanwhile, the coulomb efficiency of S/C/PEO composite reaches to ~98 % during the latter 105 cycles. The improved electrochemical performance can be attributed to the formation of PEO coating layer which can keep a tight contact between carbon and sulfur and lead to improved conductivity. Moreover, the PEO coating can act as a flexible cushion to accommodate volume changes of sulfur cathode as well as a barrier to trap soluble polysulfide intermediates during the charge-discharge processes. [ABSTRACT FROM AUTHOR]

The extraction and separation of heavy rare earths is always one of the most challenging unit operations in hydrometallurgy. Research and development of novel efficient extractant is one way to solve this problem. Organophosphinic acid is a good potential extractant. A new method was established for the synthesis of nonsymmetric dialkylphosphinic acid (NSDAPA) (R′R″POOH, R′ ≠ R″), optimized the synthesizing conditions of the key intermediate mono-alkylphosphinic acid and successfully synthesized three novel extractants ( n -octyl)(2,4,4′-trimethylpentyl) phosphinic acid, ( n -octyl)(cyclohexyl)phosphinic acid and (2,3-dimethylbutyl) (2,4,4′-trimethylpentyl)phosphinic acid. The extraction ability of the novel extractants was investigated. The structure–property relationship and the separation performance for heavy rare earth couples Er/Y, Y/Ho, Yb/Tm and Lu/Yb were evaluated. [ABSTRACT FROM AUTHOR]