Batteries and Fuel Cells
Batteries and fuel cells convert chemical energy into electrical energy using electrochemical reactions. This page summarizes principles, types, applications, a comparison table, MCQs, a quiz and FAQs useful for students.
Table of contents
- Batteries — overview & types
- Fuel cells — introduction & working
- Common examples
- Comparison
- Quiz
- MCQs
- FAQ
- References & links
Batteries: Overview and Working Principle
A battery contains one or more electrochemical cells. Each cell has an anode (oxidation), cathode (reduction) and an electrolyte to allow ion flow. During discharge electrons flow through the external circuit producing electric current while ions migrate through the electrolyte.
Types of Batteries
- Primary batteries — non-rechargeable (e.g., alkaline, zinc–carbon).
- Secondary batteries — rechargeable (e.g., lead–acid, Ni–Cd, NiMH, lithium-ion).
Fuel Cells: Introduction and Working
Fuel cells convert a supplied fuel (commonly hydrogen) and an oxidant (oxygen) directly to electricity, water and heat. They require continuous fuel and oxidant supply, and do not store energy internally like batteries.
Working of a Hydrogen Fuel Cell (PEM)
At the anode H₂ → 2H⁺ + 2e⁻. Protons pass through the proton-exchange membrane (PEM) to the cathode; electrons go through the external circuit. At the cathode O₂ + 4H⁺ + 4e⁻ → 2H₂O. Net product: water and heat.
Advantages
- High efficiency.
- Low/no harmful emissions (with pure H₂).
- Quiet, few moving parts.
- Scalable across applications.
Common Examples
- Lead-acid — automotive starter batteries (PbO₂ cathode / Pb anode / H₂SO₄ electrolyte).
- Lithium-ion — portable electronics and EVs (high energy density).
- Alkaline — household disposables (Zn / MnO₂).
Comparison Between Batteries and Fuel Cells
| Aspect | Batteries | Fuel Cells |
|---|---|---|
| Energy source | Stored chemical energy | Continuous fuel + oxidant supply |
| Rechargeability | Rechargeable (secondary) or disposable (primary) | Not rechargeable — fuel replenished continuously |
| Emissions | Varies; can produce toxic byproducts | Water & heat (when H₂ used) |
| Applications | Portable electronics, EVs, backup | Stationary power, transport, backup power |
Quiz: Batteries and Fuel Cells
Q1: What is the main difference between a battery and a fuel cell?
Answer: A battery stores chemical energy internally and supplies it until depleted; a fuel cell converts a continuously supplied fuel into electricity and does not store the chemical energy internally.
Explanation: Batteries carry reactants inside; fuel cells require external fuel feed (e.g., H₂).
Q2: Name two common types of rechargeable batteries.
Answer: Lead-acid and lithium-ion.
Explanation: Lead-acid is used in vehicles; lithium-ion in electronics & EVs due to high energy density.
Q3: What are the products of a hydrogen fuel cell reaction?
Answer: Water and heat.
Explanation: With pure H₂ + O₂, the net reaction produces H₂O and thermal energy; no CO₂ emitted.
Q4: Which part of a battery allows ions to move between electrodes?
Answer: The electrolyte.
Explanation: Electrolyte conducts ions but is electronically insulating to force electrons through the external circuit.
Q5: Give one common application of lead-acid batteries.
Answer: Vehicle starter (automobile starter batteries).
Explanation: Lead-acid offers high surge current needed to crank engines and is cost-effective.
MCQs
- What is the main product of a hydrogen fuel cell?
a) CO₂
b) H₂O
c) CO
d) CH₄
Explanation: Pure H₂ + O₂ → H₂O only. - Which battery type is commonly used in electric vehicles?
a) Alkaline
b) Lithium-ion
c) Zinc–carbon
d) Ni–Cd
Explanation: Lithium-ion provides high energy density and cycle life suited to EVs. - Which component allows ionic conduction within a battery?
a) Anode casing
b) Electrolyte
c) Separator only
d) Cathode tab
Explanation: Electrolyte provides ion paths; separator prevents electronic contact between electrodes. - Fuel cells require:
a) Stored fuel inside the cell
b) Continuous fuel and oxidant supply
c) No reactants
d) Combustion to operate
Explanation: Continuous feed of fuel (H₂) and oxidant (O₂ or air) is required. - Which is a rechargeable battery?
a) Alkaline primary cell
b) Lead-acid
c) Zinc–carbon primary cell
d) Disposable coin cell
Explanation: Lead-acid is a classic rechargeable chemistry; alkaline and zinc–carbon are usually primary (non-rechargeable).
MCQ Answers
- b) H₂O
- b) Lithium-ion
- b) Electrolyte
- b) Continuous fuel and oxidant supply
- b) Lead-acid
Frequently Asked Questions
Q: Are fuel cells better than batteries for cars?
A: It depends. Fuel cell vehicles offer fast refuelling and long range but require hydrogen infrastructure. Battery EVs are simpler where charging networks exist. Both technologies have tradeoffs in efficiency, cost and infrastructure. Q: Are lithium-ion batteries safe?
A: Modern lithium-ion cells are generally safe when used with proper battery management and thermal protection, but they can fail under abuse, overcharging, or high temperatures — proper design and safety systems are essential. Q: Where can I learn more about fuel cell designs?
A: Good starting points: manufacturer whitepapers (e.g., Ballard, Toyota), review articles in energy journals, and IEA & DOE technical reports. For a beginner, CHEMASH’s sections on electrochemistry and energy systems are helpful (internal link: Intro to Electrochemistry).
- General overview — Wikipedia: Battery
- Fuel cell basics — Wikipedia: Fuel cell
- CHEMASH internal: Energy storage & systems
