A nickel-zinc battery is a rechargeable electrochemical cell, a device that converts stored chemical energy directly into electricity. The anode, or negative terminal, of the battery is made from zinc and the cathode, or positive terminal, from nickel. Electron flow is from the anode to the cathode through the medium of an electrolyte, which provides charged particles that carry the electric current. Non-acid alkaline electrolytes are typically used in a nickel-zinc battery. Recharging reverses the electrochemical reaction and reconstitutes the original chemical structure of the cell.
Sometimes referred to by its elemental abbreviation, NiZn, the nickel-zinc battery was patented by Thomas Edison in 1901. Production capabilities of the time favored other designs and the NiZn battery was not widely implemented. The relatively high energy density, the amount of energy stored in a given volume, and the easy availability of the battery's raw materials encouraged continuing research, however.
In early versions of the nickel-zinc battery, the zinc electrode proved to be unstable over time. Zinc oxide produced by the anode formed dendrites, or filaments, in the electrolyte solution. Dendrite formation made the cell liable to short-circuiting and consequently resulted in a limited number of charge/recharge cycles. The instability also inhibited the cell's complete restoration when recharged, leading to deformation of the anode terminal.
Alkaline electrolyte solutions have been developed that stabilize the zinc electrode which, along with a polymer internal separator, overcome problems resulting from dendrite formation and terminal deformation. Advances in materials science have also enabled the production of zinc and nickel terminals that are free of heavy metal elements. A more powerful and longer lasting battery than was possible with earlier technology is the result. Recharge capability has been increased both in number of cycles and in the return of the cell to its original chemical state.
One advantage of a nickel-zinc battery is its ability to replace primary, or non-rechargeable, batteries in consumer electronics. These devices typically call for a 1.5V primary alkaline battery and would work well with the rechargeable NiZn's 1.65V nominal rating. Other rechargeable designs, such as nickel-cadmium batteries, usually have a nominal voltage of 1.2V, which could lead to device failure prior to complete battery discharge.
The nickel-zinc battery is seen as an environmentally friendly alternative to more common designs. Nickel and zinc are both relatively abundant and each can be fully reclaimed by recycling. Mercury, cadmium, lead or other toxic metals are not used in its production, nor are there any flammable or corrosive active materials.