Batteries & Fuel cells


Disposable batteries

ChemistryAnode (−)Cathode (+)Nominal voltage
Specific energy
Alkaline (zinc–manganese dioxide)ZnMnO21,150.4–0.59
Lithium (lithium–iron disulphide) LiFeS2LiFeS21,51,07
Silver-oxide (silver–zinc)ZnAg2O1,50,47

Rechargeable batteries

Chemical compoundsCell voltage
Specific energy
Lithium ion4,2-3.60,46

Thermal efficiency - Fuel cells

Fuel Cell TypeOperating TemperatureSystem OutputEfficiencyApplications
Alkaline (AFC)90–100oC
10kW–100kW60–70% electric• Military
• Space
Phosphoric Acid (PAFC)150–200oC
(250kW module typical)
80–85% overall with combined heat and
power (CHP) (36–42% electric)
• Distributed generation
Polymer Electrolyte Membrane or Proton Exchange Membrane (PEM)*50–100oC
<250kW50–60% electric• Back-up power
• Portable power
• Small distributed generation
• Transportation
Molten Carbonate (MCFC)600–700oC
(250kW module typical)
85% overall with CHP (60% electric)• Electric utility
• Large distributed generation
Solid Oxide (SOFC)650–1000oC
5kW–3 MW85% overall with CHP (60% electric)• Auxiliary power
• Electric utility
• Large distributed generation
The table indicates the thermal efficiency for various types of fuel cells based on the higher heating value for hydrogen.

Gibbs free energy - Fuel cells

Form of water productTemp oC∆g ̄f kJ/moleMax EMFEfficiency limit
Liquid25-237,21.23V83 %
Liquid80-228,21.18V80 %
Gas100-225,31.17V79 %
Gas200-220,41.14V77 %
Gas400-210,31.09V74 %
Gas600-199,61.04V70 %
Gas800-188,60.98V66 %
Gas1000-177,40.92V62 %
The table above indicates the amount of free energy by applying Gibbs function at various states.