Nickel–zinc accordion-fold batteries with microfibrous electrodes using a papermaking process

Thin microfibrous substrates were built using a low cost, high speed, wet lay papermaking process with nickel and copper microfibers. High quality microfiber sheets with designed thickness and void volumes were fabricated at the Center for Microfibrous Materials Manufacturing at Auburn University. Products include thin microfibrous nickel and copper substrates with or without suitable expanded metal meshes, either sandwiched inside or on the backside. An improved method for fabrication of zinc electrodes was accomplished by electro-depositing active zinc material on 6 and/or 9 μm diameter microfibrous copper substrates. These zinc electrodes with various additives were examined for shape change and tested for performance. A new structure of electrode design was employed using an accordion-fold cell. By using five individual segments sintered onto an expanded metal mesh, an accordion-fold cell (670 mAh rated capacity) was assembled and had 98.0% coulomb efficiency, 88.6% energy efficiency at 72% depth-of-discharge (DOD) and 73.2% state-of-recharge (SOR) in the 79th cycle. A Ni–Zn cell consisting of one thick nickel and one thick zinc electrode was tested for rate performance in comparison with the 670 mAh accordion-fold cell. The accordion-fold cell (1279 mAh rated capacity) was scaled-up and tested for 835 cycles at 38% DOD at a 0.3 C charge and discharge rates, and continuously operated at 38% DOD until the 1050th cycle was finished at 0.16 C charge/discharge rates. A 7115 mAh accordion-fold demonstration cell was tested at 0.28 C charge and discharge rates for 608 cycles and still had a 4.7 Ah capacity at a 0.08 C discharge rate.