Commercialization of rechargeable zinc electrodes has been desirable goal for decades. Theoretical specific energy of the zinc electrode is 984Wh/kg, and energy density 7026Wh/L. Zinc electrodes can be used for nickel-zinc, silver-zinc, zinc-air and zinc-manganese dioxide batteries.
Silver-zinc batteries are expensive because of the silver cathodes. Zinc-air batteries are the cheapest in relation to specific energy, and have energy densities comparable to lithium power sources. However, the recharging efficiencies are about 0.5-0.6, and outside humidity has significant influence on battery performance.
Nickel-zinc and manganese dioxide cathodes are the best to combine with zinc. The nickel-zinc batteries have exclusive power capabilities, 85%-90% recharging efficiency, and acceptable self-discharge. Numerous attempts to implement nickel-zinc system have been unsuccessful because extensive corrosion, gas evolution, the growth of dendrites, and volume changes of the zinc electrodes.
Panisolar has overcome these problems, and have demonstrated 800 cycles of charge-discharge of the nickel-zinc batteries. The utilization of the zinc cartridges makes the nickel-zinc batteries strong competitors with lead-acid and lithium storage devices. Periodical replacement of zinc cartridges at about 5%-15% of the battery cost (instead of disposing of the battery) can increase battery cycle life to about 20,000 cycles. Panisolar has proposed flat batteries to be mounted on the walls of buildings. The storage devices that are only 1cm-2cm thickness save interior space, and make the nickel-zinc batteries the prime choice when safety is a major concern.