UPSC Prelims 2025 Q43: Science & Technology – Technology
- (a) Only one
- (b) Only two
- (c) Only three
- (d) All the four
Answer: (c) Only three
Explanation
Battery Elements - Cathode vs Anode:
| Element | Battery Location | Role | In Cathode? |
|---|---|---|---|
| Cobalt (I) | CATHODE | Stabilises crystal structure in NMC/NCA batteries | YES |
| Graphite (II) | ANODE | Intercalates lithium ions during charging - stores charge | NO - anode only |
| Lithium (III) | CATHODE (also in electrolyte salt) | Active ion in LiCoO₂, NMC, LFP cathode materials | YES |
| Nickel (IV) | CATHODE | Increases energy density in NMC (Nickel-Manganese-Cobalt) batteries | YES |
Common cathode chemistries:
NMC = Nickel + Manganese + Cobalt + Lithium.
NCA = Nickel + Cobalt + Aluminum + Lithium.
LFP = Lithium + Iron + Phosphate (no cobalt or nickel).
Graphite is the standard ANODE material — it is not in the cathode.
Answer: (c) Only three.
Why each option is right or wrong
- (a) Incorrect. Only one element (graphite) is excluded from cathodes — three elements (cobalt, lithium, nickel) are standard cathode components.
- (b) Incorrect. Three elements are in cathodes, not two.
- (c) CORRECT. Cobalt, Lithium, and Nickel all appear in standard cathode chemistries (NMC, NCA). Graphite is the anode material and is never in the cathode.
- (d) Incorrect. Graphite is definitively an anode material — it intercalates lithium ions at the negative electrode.
Key point
Cathode = Cobalt + Lithium + Nickel (NMC/NCA). Anode = Graphite. Graphite stores Li⁺ ions during charging — NOT a cathode material.
Remember
Graphite = ANODE. Cobalt + Lithium + Nickel = CATHODE. Three of the four listed elements are cathode materials.
Common mistakes
- Placing graphite in the cathode — graphite is the most common anode material in all lithium-ion batteries. Classic UPSC trick question.
- Not knowing cobalt shortage is a critical EV supply chain issue because cobalt is an essential cathode element, often mined in conflict zones (DRC).
- Confusing LFP batteries (no cobalt, cheaper) with NMC batteries (has cobalt, higher energy density).
Exam tip
Battery memory trick: Anode = Graphite (G = Gives away electrons on discharge). Cathode = Cobalt + Lithium + Nickel. Critical mineral supply concerns = cobalt + lithium + nickel — all cathode materials.
Sources
- IEA — The Role of Critical Minerals in Clean Energy Transitions (2021)
- Ministry of Mines — Critical Minerals List India
- NCERT Class XII — Chemistry (Electrochemistry, Batteries)