Electrochemical energy systems – Battery vs. fuel cell: How does a conventional battery fundamentally differ from a fuel cell in operation and design?

Introduction / Context:
Batteries and fuel cells both convert chemical energy to electrical energy, but their architectures and sources of reactants differ. This distinction affects applications from portable devices to vehicles and grid storage.

Given Data / Assumptions:

• Batteries contain their active materials internally.
• Fuel cells receive fuel and oxidant from external supplies.
• No specific chemistry (lead acid, Li-ion, PEMFC, SOFC) is mandated by the question.

Concept / Approach:
A battery is generally a closed or self-contained system: its electrodes and electrolyte hold the necessary reactants. When discharged, internal reactants are consumed and require recharging or replacement. A fuel cell is an open system: it continuously generates electricity while fuel and oxidant are fed from outside. When the feeds stop, power stops even though the cell hardware remains unchanged.

Step-by-Step Solution:
Identify the defining difference: internal versus external reactant supply.Select the option that states a battery is a closed system.

Verification / Alternative check:
Consider a car: the 12 V battery stores reactants and is recharged; a fuel cell vehicle carries hydrogen and draws oxygen from air, producing water continuously while fuel flows.

Why Other Options Are Wrong:

• Hydrogen and oxygen use: that is characteristic of many fuel cells, not of all batteries.
• Polymer electrolyte membrane: specific to certain fuel cells; many batteries do not use PEM.
• Fuel cell storing all reactants internally: incorrect; fuel cells are designed for continuous external feed.

Common Pitfalls:
Assuming any device with electrodes and electrolyte is closed; the key is whether reactants are replenished externally during operation.

Final Answer:
A battery is a closed system