An Electrochemical and XRD Study of Lithium Insertion into Mechanically Alloyed Magnesium Stannide

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Abstract
The intermetallic Mg2SnMg2Sn is a promising negative electrode material for rechargeable lithium cells. Preliminary cycling tests have demonstrated stable capacities at 400 mAh/g for 20 cycles. Magnesium stannide was produced by mechanically alloying magnesium and tin powders. Mechanical alloying can convert the equilibrium Mg2SnMg2Sn phase to a metastable phase by the introduction of defects with extended milling times. In situ X-ray diffraction has shown that the cubic Li2MgSnLi2MgSn phase, which is similar in size and structure to cubic Mg2Sn,Mg2Sn, is produced by lithium insertion into the equilibrium and metastable phases. The conversion from the metastable phase is irreversible, so subsequent lithium removal from Li2MgSnLi2MgSn produces the equilibrium Mg2SnMg2Sn phase. © 2003 The Electrochemical Society. All rights reserved.