Electrochemical performances of MgH2 and MgH2-C films for lithium ion battery anode

摘要

As a high-capacity hydrogen storage material, MgH2 also shows specific advantages for LIB anode. In this work, MgH2 and MgH2-C films were prepared by magnetron sputtering and hydrogenation treatment, and their microstructural and electrochemical properties were investigated. Through the conversion reaction of MgH2 with lithium (MgH2 + 2Li(+) -> Mg + 2LiH), the reversible lithium storage was achieved in the MgH2 and MgH2-C films. The MgH2 film delivers the initial discharge capacity of 313.9 Ah cm(-2) (similar to 2956 mAh g(-1)), the discharge and charge capacities related to the conversion process are respectively 150.0 mu Ah cm(-2) (similar to 1412 mAh g(-1)) and 55.0 mu Ah cm(-2) (similar to 518 mAh g(-1)), with the inefficiency of 63.3%. The GITT measurement determined the equilibrium potential of this conversion reaction to be 0.55 V vs. Li/Li+, and the voltage hysteresis between discharge and charge is only 10 mV vs. Li/Li+. In comparison with the MgH2 film, the MgH2-C film has smaller crystallite size, lower polarization effect and structural stability, but exhibiting lower capacity and equally poor cyclic performance. The poor cycle life of MgH2-C film electrode is due to the large irreversibility of conversion reaction of MgH2 instead of structural damage of film electrode during cycling. (C) 2017 Elsevier B.V. All rights reserved.