Electrochemical Properties Of A₂B Hydrogen Storage Alloy With Conductive Polymer Surface Treatment

Mg-based A2B type hydrogen storage alloys have been received extensive interest onNi/MH battery as negative electrode due to their low density, high hydrogen storagecapacity and rich resources. Mg chemical character is very active, once form the surfaceoxide layer caused poor charge and discharge cycle stability, poor dynamic performance,antierosion ability and other short comings in alkaline solution. In this paper, we studiedthe chemical oxidation method prepare conductive polymer polyaniline, polypyrrole andpolythiophene surface treatment influence on the electrochemical properties ofMg1.8Nd0.2Ni hydrogen storage alloy. The surface morphology of hydrogen storage alloywas analyzed by SEM, the electrochemical properties of the alloys were tested byelectrochemical testing system. It mainly representation the effects by surface treatment onthe surface charge transformation, bulk hydrogen diffusion in alloy charge and dischargeprocess.Study found that after surface treatment, the alloy surface is covered with conductivepolymer layer. After this polyaniline treatment process, the hydrogen storage alloy rate ofdischarge capacity retention increased from77.82%to86.31%after50charge anddischarge cycles. But the surface treatment bring about a certain hinder of the alloy surfacecharge transfer. Surface treatment process has positive impact on Mg2Ni based hydrogenstorage alloy dynamic performance reaction retardation. The polymer layer to preventspenetration of oxygen atomic, reduce the volume expansion, reducing alloy powder, bulkhydrogen diffusion rate increased significantly and have a positive effect on the corrosionresistance of alloy.Used silane coupling agent enhancement of surface treatment effect, effectivelyimprove the cycling stability. The PPy surface treatment hydrogen storage alloy capacityretention rate increased from77.82%to91.21%. Polythiophene surface treatment reducedthe surface charge transfer impedance, which is concerned with the structural properties of polythiophene polymer density, high strength polythiophene, collector has a significanteffect on formation of alloy surface charge transfer.