Highly Reversible Sn-Co Alloy Anode Using Porous Cu Foam Substrate for Li-Ion Batteries

A three-dimensional Sn-Co alloy electrode is prepared on porous Cu foam by electrodeposition, and its electrochemical properties are investigated by galvanostatic charge/discharge tests. The effects of the Cu foam substrate and Co alloying on the morphological and phase structural changes with cycles are examined by ex situ SEM observation and XRD analysis. The Sn-Co alloy electrode exhibits an outstanding cyclic performance with a high coulombic efficiency compared with the electrochemical performance of a pure Sn electrode deposited on a smooth Cu sheet. Ex situ SEM analysis reveals that the porous Cu foam not only inhibits the pulverization and delamination of the Sn-Co alloy from the substrate by enhancing the bond between them, but also accommodates the volumetric expansion of the active phase. Moreover, the nonequilibrium CoSn2 phase formed on the Cu foam substrate reversibly reacts with Li without structural deterioration, and hence remains unchanged for 50 cycles. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.050211jes] All rights reserved.