The Refuelable Zinc-air Battery: Alternative Techniques for Zinc and Electrolyte Regeneration
An investigation was conducted into alternative techniques for zinc and electrolyte regeneration and reuse in the refuelable zinc/air battery that was developed by LLNL and previously tested on a moving electric bus using cut wire. Mossy zinc was electrodeposited onto a bipolar array of inclined Ni plates with an energy consumption of 1.8 kWh/kg. Using a H{sub 2}-depolarized anode, zinc was deposited at 0.6 V (0.8 kA/m{sup 2}); the open circuit voltage was 0.45 V. Three types of fuel pellets were tested and compared with results for 0.75 mm cut wire: spheres produced in a spouted bed (UCB); coarse powder produced by gas-atomization (Noranda); and irregular pellets produced by chopping 1-mm plates of compacted zinc fines (Eagle-Picher, Inc.). All three types transported within the cell. The coarse powder fed continuously from hopper to cell, as did the compacted pellets (< 0.83 mm). Large particles (> 0.83 mm; Eagle-Picher and UCB) failed to feed from hopper into cell, being held up in the 2.5 mm wide channel connecting hopper to cell. Increasing channel width to {approx}3.5 mm should allow all three types to be used. Energy losses were determined for shorting of cells during refueling. The shorting currents between adjacent hoppers through zinc particle bridges were determined using both coarse powder and chopped compressed zinc plates. A physical model was developed allowing scaling our results for electrode polarization and bed resistance Shorting was found to consume < 0.02% of the capacity of the cell and to dissipate {approx}0.2 W/cell of heat. Corrosion rates were determined for cut wire in contact with current collector materials and battery-produced ZnO-saturated electrolyte. The rates were 1.7% of cell capacity per month at ambient temperatures; and 0.08% of capacity for 12 hours at 57 C. The total energy conversion efficiency for zinc recovery using the hydrogen was estimated at 34% (natural gas to battery terminals)--comparable to fuel cells. Producing zinc shot was quoted at 1.5-3 cents/lb above base price (52 cents/lb, ASM) for super purity ingot. Both the spouted-bed and the Eagle-Picher processes might conceivably be configured for fleet operation in user-owned and operated equipment located a the fleet's home base. This would eliminate the need for green-field industrial plants and fuels distribution systems. Scaleup of the spouted bed process and detailed examination of the Eagle-Picher process are recommended.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 898511
- Report Number(s):
- UCRL-TR-218414; TRN: US200708%%118
- Country of Publication:
- United States
- Language:
- English
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