Chemical and electrochemical dehydriding characteristics of TiV2.1Ni0.3-Raney Ni composite prepared by ball-milling in the presence of a reducing agent

Composite particles represented as TiV2.1Ni0.3-Raney Ni(R) were prepared by ball-milling a TiV2.1Ni0.3 alloy with Raney Ni in the presence of 0.01 M sodium hypophosphite (NaH2PO2) aqueous solution as a reducing agent. The composite particles had different morphology from original TiV2.1Ni0.3 alloy particles and TiV2.1Ni0.3-Raney Ni composite particles prepared by the ball-milling in the absence of the NaH2PO2 aqueous solution. In charge-discharge cycle tests, the TiV2.1Ni0.3-Raney Ni(R) composite electrode showed the maximum discharge capacity of 620 mAh g(-1), while its cycle durability was similar to the TiV2.1Ni0.3 alloy electrode, which was explained from depth profiles of constituent elements by Auger electron spectroscopy (AES). In thermogravimetry (TG) and differential thermal analysis (DTA), two steps of dehydriding for hydrided TiV2.1Ni0.3-Raney Ni(R) composite started from much lower temperature than hydrided Ti2.1Ni0.3 alloy, and the amount of hydrogen absorbed in this composite was still larger than that absorbed in the TiV2.1Ni0.3-Raney Ni composite. (C) 2003 Elsevier B.V. All rights reserved.