MICROSTRUCTURES AND ELECTROCHEMICAL PROPERTIES OF RAPIDLY-SOLIDIFIED Si-Mn ALLOY

Abstract

The microstructure and electrochemical properties of a Si(70)Mn(30) alloy prepared by melt spinning and arc melting have been investigated. Melt-spun ribbons and arc-melted ingots were fragmented and mixed with acetylene black (AB), polyvinylidene fluoride (PVDF), and N-methylpyrrolidinone by planetary milling for 2 h to characterize their electrochemical properties. The results showed that the microstructures of the melt-spun ribbons represented a fine eutectic constituent composed of a silicon phase with a thickness of approximately 50 similar to 70 nm and a Mn(4)Si(7) compound. The cyclic behavior of the rapidly solidified melt-spun Si(70)Mn(30) ribbons improved remarkably over that of the arc-melted specimens because of a finer microstructural scale; as the thickness of silicon crystal decreased 40 fold, the initial irreversible capacity was reduced by more than 2.5 times. The improved cycle performance of the melt-spun ribbons is a consequence of the small diffusion distance for the lithium-ion exchange.