Solid-state Mg/MnO2 cell employing a gel polymer electrolyte of magnesium triflate

In view of the abundant resources, low costs and the relatively low reactiv ity of magnesium, solid-state batteries using this metal are worthy of inve stigation in comparison with solid-state lithium batteries. For such cells, a gel polymer electrolyte (GPE) is prepared using polyacrylonitrile, propy lene carbonate, ethylene carbonate and magnesium triflate. The composition of GPE is optimized in view of the minimum Liquid components required for g el formation and maximum ionic conductivity. This is achieved by preparing several films with varying concentration of the constituents and measuring their ionic conductivity by AC impedance spectroscopy. Mg/GPE/MnO2 cells ar e assembled and their discharge behaviour is studied. A capacity value of a bout 40 mA h per gram of MnO2 is obtained. Cyclic voltammetric experiments demonstrate qualitatively the reversible behaviour of the MnO2 electrode. T he Mg/GPE/MnO2 cells are subjected to about 20 charge-discharge cycles with a consistent capacity of about 20 mA h g(-1) Cycle-life data is limited by surface passivation of the magnesium negative electrode and poor rechargea bility of the MnO2 positive electrode. At present, the results show that th e Mg/GPE/MnO2 cells have an inferior performance in comparison with that of well-developed, lithium-based rechargeable batteries. Further extensive in vestigations are required to raise the performance of the magnesium-based r echargeable cells to practical levels. (C) 2000 Elsevier Science S.A. All r ights reserved.