A lightweight nickel composite electrode I: Concept and feasibility

Abstract

Composite metal—matrix materials, successful in various structural component applications, have not been widely employed to solve electrochemical energy storage problems. The electrical efficiency, durability, and relatively high energy density of alkaline battery systems makes development of an improved sintered nickel electrode advantageous. Modification of current fabrication methods, however, should be targeted at a lightweight, long-life, low cost product, to be of any significant value. The nickel composite electrode (Ni.C.E.) is fabricated by coating a graphite mat fiber material with a thin (0.6 – 1.0 μm) nickel layer and sintering to a compact structure. The resulting lightweight, durable composite structure is producible in porosities of 55 to >90%. This porous structure has been impregnated electrochemically with active material to a level of 200 A h/kg. Test cells, containing single composite positives coupled with commercial negatives, exhibited lives approaching 800 cycles under a demanding cycling regime. The composite nickel electrodes showed utilizable gravimetric energy densities of 125 – 175 A h/kg under the test conditions. ap ]The composite electrodes in multi-plate cells cycled under similar conditions had good capacity retention for 500 or more cycles. A gravimetric energy density of 120 – 125 A h/kg was noted for the entire positive plate block assembly including terminal. This is an increase of 66 – 72% over that measured for commercial positives. Volumetric energy densities for the Ni.C.E. are roughly equivalent to those of powder sinters. No detrimental effects due to the presence of graphite have been noted. Further optimization of this system may produce electrodes of still higher energy density.