Better Cycling Performances of Bulk Sb in Na-Ion Batteries Compared to Li-Ion Systems: An Unexpected Electrochemical Mechanism

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• 作者：Ali Darwiche ; Cyril Marino ; Moulay T. Sougrati ; Bernard Fraisse ; Lorenzo Stievano ; Laure Monconduit
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：December 26, 2012
• 年：2012
• 卷：134
• 期：51
• 页码：20805-20811
• 全文大小：484K
• 年卷期：v.134,no.51(December 26, 2012)
• ISSN：1520-5126

文摘

Pure micrometric antimony can be successfully used as negative electrode material in Na-ion batteries, sustaining a capacity close to 600 mAh g^鈥? at a high rate with a Coulombic efficiency of 99 over 160 cycles, an extremely high capacity compared to any other compound tested against both Li and Na. The reaction mechanism with Na does not simply go through the alloying mechanism observed for Li where the intermediate species are those expected from the phase diagram. In the case of Na, the intermediate phases are mostly amorphous and could not be precisely identified. Surprisingly, we evidenced that a competition takes place at the end of the discharge of the Sb/Na cell between the formation of the hexagonal and the cubic polymorphs of Na₃Sb, the last being described in the literature as unstable at atmospheric pressure and only synthesized under high pressure (1鈥? GPa). In addition, fluoroethylene carbonate added to the electrolyte combined with an appropriate electrode formulation based on carboxymethyl cellulose, carbon black, and vapor ground carbon fibers seems to be determinant in the excellent performances of this material.