Control of Mg-Based Hydrogen Storage Alloy Nanocrystallites and Their Surface Modification

The results obtained in this study for three years are summarized as follows.1。XPS and Raman spectroscopy showed that electron transfer from graphite withπelectrons to the oxidized surface Mg by ball-milling weakened the Mg-O bond strength，leading to the formation of the Ni-O bonding.The ratio of metallic Ni to Mg on the MgNi surface was increased by the ball-milling.2。The rate of hydrogen absorption for Mg-D22-D2Ni-70wt.%Ni composite at 30℃markedly increased in comparison with Mg D22-D2Ni-70wt.%mixture and the amount of absorbed hydrogen reached H/M of about one within1h.In the charge-discharg test，the Mg I D22e D2 Ni-70wt.%Ni composite showed markedly high discharge capacity of about 870mAh g Mg D2Ni-D1.The discharge capacity，moreover，increased up to 1080mAh g(Mg I D22 I D 2 Ni)I D1-1 by using Ni powder with the weight ratio of Ni to alloy of 10 instead of Cu powder.The charge-discharge cycle performance was improved by increasing the amount of added Ni powder.3。The charge-discharge cycle performance for Mg I D 20.9 I D 2 M I D 20.1 I D 2 Ni(M=Ti，V)alloys was greatly improved in comparison with MgNi though the initial discharge capacity decreased.This was ascribed to the preference dissolution of V component in alkaline solution for the Mg I D 20.9个D 2V I D 20.1个D 2Ni alloy and the formation of Ti oxides on the alloys surface for the Mg y D 20.9个D 2Ti个D 20.1个D 2 Ni alloy.In addition，Mg I D 20.9 I D 2 Ti I D 2 x D 2 V I D 20.1-x D 2 Ni alloy showed cycle performance superior to the Mg I D 20.9 I D 2 M I D 20.1 I D 2 Ni(M=ti，v)alloys due to the synegret effect of V and Ti components.

The results obtained in this study for three years are summarized as follows.1. XPS and Raman spectroscopy showed that electron transfer from graphite with π electrons to the oxidized surface Mg by ball-milling weakened the Mg-O bond strength, leading to the formation of the Ni-O bonding. The ratio of metallic Ni to Mg on the MgNi surface was increased by the ball-milling.2. The rate of hydrogen absorption for MgィイD22ィエD2Ni-70 wt.% Ni composite at 30℃ markedly increased in comparison with MgィイD22ィエD2Ni and MgィイD22ィエD2Ni-70 wt.% mixture and the amount of absorbed hydrogen reached H/M of about one within 1 h. In the charge-discharg test, the MgィイD22ィエD2Ni-70 wt.% Ni composite showed markedly high discharge capacity of about 870 mAh g(MgィイD22ィエD2Ni)ィイD1-1ィエD1. The discharge capacity, moreover, increased up to 1080 mAh g(MgィイD22ィエD2Ni)ィイD1-1ィエD1by using Ni powder with the weight ratio of Ni to alloy of 10 instead of Cu powder. The charge-discharge cycle performance was improved by increasing the amount of added Ni powder.3. The charge-discharge cycle performance for MgィイD20.9ィエD2MィイD20.1ィエD2Ni (M=Ti, V) alloys was greatly improved in comparison with MgNi though the initial discharge capacity decreased. This was ascribed to the preference dissolution of V component in alkaline solution for the MgィイD20.9ィエD2VィイD20.1ィエD2Ni alloy and the formation of Ti oxides on the alloys surface for the MgィイD20.9ィエD2TiィイD20.1ィエD2Ni alloy. In addition, MgィイD20.9ィエD2TiィイD2xィエD2VィイD20.1-xィエD2Ni alloy showed cycle performance superior to the MgィイD20.9ィエD2MィイD20.1ィエD2Ni (M=ti, v) alloys due to the synegret effect of V and Ti components.