Effect Of Additive And Binder On The Properties Of Metal-Hydride Electrode

Ni/MH battery is the third generation of practical secondary battery. The pasting method, with the nickel-plated punched steelband (NPPS) as the substrate of metal-hydride(MH) electrode has such advantages as low cost and continuous production. However, additive is indispensable and more binder is necessary in the preparation of MH electrode. Following the review of research on additive and binder, aimed at the application in the mass production. the effect of additive arid binder on the properties of metal-hydride in the vented cell was investigated respectively.In the study on additive, metal powder including superfine nickel powder(T210 and 125 5),copper powder and nickel fiber, acetylene black and cobalt oxide(CoO) were involved. The results show copper powder and nickel fiber are not fit as additive to MH electrode ; 10?5 percent superfine nickel powder, namely T2 10 or 1255, 0.7 percent acetylene black or 2 percent CoO can be used effectively. Among them, the electrode containing superfine nickel powder shows the lowest specific capacity and the second highest capacity density. The electrode added with acetylene black shows the highest specific capacity and the lowest capacity density. The electrode added with 4? percent CoO shows self-discharge and thus capacity decay in the initial cycles, caused by the micro-short circuit due to the formation of obalt bridge? the electrode containing 2 percent CoO shows rather stable in the cycle than the former two, but self-discharge still occurs in some degree.In the study on binder, the electrodes bonded by polytetrafluoroethylene(PTFE), polyvinyl aleohol(PVA) and natural latex(NL) were investigated respectively. The PTFE-bonded metal-hydride electrode is unsatisfactory. The PVA-bonded electrode,dried in the temperature above 600(2, shows poor strength; but if dried in the room temperature. the electrode bonded by 1?1.5 percent PVA is satisfactory in terms of preparation as well as the electrochemical properties. The electrode bonded by 0.7 percent NL and 0.3 percent carboxymethyl cellulose sodium(CMC) is pliable, even dried in the temperature of 850(2 .but is inferior to the PVA-bonded electrode in the electrochemical properties.