Zinc Air and Zinc Ferricyanide Batteries
Source: Lawrence Livermore National Laboratory
Date: 1/1/95    Record No.: 10082
Contact: John F. Cooper, 510-423-6649

Zinc Air and Zinc Ferricyanide Batteries
LLNL is developing a new battery technology that can be used to propel electric vehicles (zinc/air battery) or provide energy storage for utilities or remote power installations (zinc/ferricyanide battery). Both batteries use a self-feeding cell, an LLNL invention, which consumes pellets of zinc fed from an external storage tank.

Zinc Air Battery
Livermore has built a Zn Air battery test stack of 6 cells that they are installing in a borrowed city transit bus to demonstrate operation in an actual vehicle.

The concept is a battery that can be refueled in minutes, with a supply of Zinc pellets, permitting continuous 24-hour usage of service vehicles. Such fleet or on-site applications (transit, shuttle buses, taxis, airport vehicles, fork lifts, etc.) would support the infrastructure to recycle the zinc. The refueling takes place with the pellets entrained in a flowing liquid solution (not a "slurry"), and the spent fuel is pumped out of the battery as a milky suspension of zinc oxide.

A battery, together with its "charger," is estimated to be cost competitive with Pb Acid, at $60/kW plus $2/kWh.

Oil companies should be interested because this system can use natural gas as the primary fuel, making H2 and electricity to perform the reycling/recharging (zinc oxide to zinc). With hydrogen, the process can be done using much less electricity, and thus provide fuel-cell type efficiencies at much lower cost.

Note: the chemistry of this cycle has been successfully implemented in an Israeli system installed on German post office vehicles. However, that battery is not refuelable because its electrodes must be removed and replaced, and shipped to a factory for recycling.

While some observers express concern about any system with active components (e.g., pumps, tubing etc.), advocates point out that the current ICE automobile has dozens of auxiliary systems, and that the real issue is cost and performance, which they are confident can be demonstrated by zinc batteries.

Interested parties are waiting for the results of the on-board test of the multi-cell stack. Although the recharging/recovery unit has yet to be built, its processes have been demonstrated.

Zinc Ferricyanide Battery
This battery would use the same anode and zinc/recovery scheme, but would store the ferricyanide externally and use a porous carbon block for the cathode, eliminating the air cathode and its voltage loss. The battery would be appropriate for load leveling and long-term storage of energy; e.g., for remote opportunity power (wind, solar).

The chemistry is well known. Lockheed developed a battery long ago that stored only the ferricyanide outside the battery, and had operational limitations that prevented attaining adequate efficiency. The new design concept will provide for storage of both ferricyanide and zinc pellets external to the battery, allowing energy storage and power to be independently matched to the application, and making the higher efficiency attainable in practice. (The turn-around efficiency of Zinc Ferri. is about 84% compared to 63% for PbAcid.)

The work has been funded by the Dept. of Transportation and Calstart. There is no DOE money in this program. DOE, through its ABC effort, will not undertake any refuelable battery concepts. (DU, Distributed Utility)