In this article at OpenGenus, we have explored the concept of Battery and Fuel cells including different types of batteries, performance requirements, hydrogen-oxygen fuel cells and much more.

Table of contents

• Battery
• Types of batteries
• Primary batteries
• Secondary storage or accumulator batteries
• Performance Requirements of a battery for commercial requirements
• Fuel Cells
• Characteristics of Fuel Cells
• Requirements for successful functioning of a fuel cells
• Hydrogen-oxygen Fuel Cell
• Molten Carbonate Fuel Cell
• Solid Oxide Fuel Cell

Battery

• Device that stores energy
• That energy is converted from chemical energy to electrical energy
• Portable source of electrical energy

Types of batteries

• Primary batteries
• Secondary storage or accumulator batteries

Primary batteries

• Disposable batteries as cannot be recharged
• Source of dc power
• Convenient to use
• Cost efficient

Secondary storage or accumulator batteries

• Can be recharged after partial or complete discharge
• Source of dc power
• Supply to large, short-term(or small, long-term) power requirements as in automobiles and airplane batteries
• Capacitance is large which is beneficial to circuits as in telephone exchanges

Performance Requirements of a battery for commercial requirements

• Long shelf life
• Reliability
• High energy efficiency
• Tolerance to different environmental conditions such as variation in temperature, vibration, shock, etc.
• High capacity

Fuel Cells

• Similar to other electrochemical cells
• Only difference is that chemical energy is provided by fuel and oxidant is stored outside the cell
• Capable of supplying current as long as the reactants are supplied
• Primary cell

Characteristics of Fuel Cells

• Noise levels are low
• High efficiency
• Free from vibration , heat transfer and thermal pollution
• Modular and hence can be built in a wide range of power requirements
• Emission levels are far below the permissible limits

Requirements for successful functioning of a fuel cells

• Fuel and oxidants must be cheap and readily available
• To promote high rate of electrode processes, high temperature and suitable catalyst is required
• Fairly concentrated aqueous solutions of the electrolytes should be used to have good conductivity and minimize the effect of concentration polarization
• Suitable fuel design so that there is a stable interface between solid electrode, liquid electrolyte and gaseous fuel which promotes high rate of electrode processes

Hydrogen-oxygen Fuel Cell

• Consists of two inert porous electrodes(made of either graphite saturated with finely divided Platinum or a 75/25 alloy of Pd with Ag or Ni) and an electrolyte solution of 25% KOH solution.

• Hydrogen gas is bubbled through anode

• Oxygen gas is bubbled through cathode

• Following are the reactions:

• At anode:
  

• At cathode:
  

• Net:
  

• The product discharged by the cell is water

• Standard emf of cell is found to be 1.23V(Eox+Ered=0.83V+0.40V)

• In actual practice, emfof cell is 0.8 to 1.0V.

• A number of fuel cells are stackedtogether in series to make a Fuel cell battery or fuel battery.

Uses of Hydrogen-oxygen Fuel Cell

• Auxiliary energy source in spce vehicles
• Product water is a valuable source of fresh water for astronauts
• Preferred for space craft due to their lightness

Molten Carbonate Fuel Cell

Advantages

• Higher efficiency
• No noble metal catalyst
• No negative effects from CO or CO2(High temperature increases O2 kinetics)
• Internal reforming(H2 OR CH4)

Disadvantages

• Material is resistant to degradation at high temperature.

Solid Oxide Fuel Cell

Advantages

• Internal reforming
• Solid electrolyte eliminates leaks
• CO and CO2 are not problematic
• H2O management, catalyst flooding, slow O2 kinetic are not problematic

Problems

• Material constraints due to high temperature