Electrochemical properties and structure of MlNi_5-xSn_x system

Qin Lin, Dajian Zhu, and Shuang ZhaoMetallurgy School, University of Science and Technology Beijing, Beijing 100083, China

摘 要：<正>The electrochemical properties and structure of M1Ni5-xSnx（x=0-0.5） hydrogen storage alloys were investigated by pressure-composition isotherms, electrochemical measurements, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and atomic parameters. With a small amount of tin substitution, the cycle life increases by 52% （0.5C） and 42% （1.0C）, but maximum discharge capacity decreases only by 3.0% and 3.5%, respectively. The cycle life is obviously improved by the low volume expansion and the formed SnO2 surface layers upon electrochemical cycling. The substitution of Ni by Sn leads to an increase of the unit cell volume and charge-discharge cycle life and decrease of the plateau pressure, hysteresis and the hydrogen storage capacity. The standard enthalpy of hydride formation decreases with increasing tin substitution. The main factor that influences the standard enthalpy of the hydriding reaction is the number of the outer orbit electrons and not the atomic size factor.

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