In the context of electric vehicle batteries, consider the following elements :

I. Cobalt
II. Graphite
III. Lithium
IV. Nickel

How many of the above usually make up battery cathodes?

(a) Only one
(b) Only two
(c) Only three
(d) All the four

The correct answer is (c) Only three.

Explanation

Here is a breakdown of the role each element plays in a typical lithium-ion electric vehicle battery:

I. Cobalt:(Used in Cathodes) Cobalt is a key component in many high-energy-density cathodes. It helps stabilize the battery’s structure, improving its lifespan and safety. It is a main ingredient in NMC (Lithium Nickel Manganese Cobalt Oxide) and NCA (Lithium Nickel Cobalt Aluminum Oxide) cathodes.
II. Graphite:(Not used in Cathodes) Graphite is the most common material used to make the anode (the negative electrode), not the cathode. Its layered structure is excellent at holding lithium ions when the battery is charged.
III. Lithium:(Used in Cathodes) This is the fundamental element of the battery. The cathode is a compound (typically a metal oxide) that contains lithium. The battery works by the movement of lithium ions ([latex]Li^+[/latex]) from the cathode to the anode during charging and back to the cathode during discharging.
IV. Nickel:(Used in Cathodes) Nickel is a primary component in the most common EV battery cathodes, NMC (Lithium Nickel Manganese Cobalt Oxide) and NCA (Lithium Nickel Cobalt Aluminum Oxide). A higher nickel content generally leads to a higher energy density, which means a longer range for the vehicle.

Therefore, three of the four elements listed—Cobalt, Lithium, and Nickel—are usually used to make up battery cathodes.

Learn More

How a Lithium-Ion Battery Works

A lithium-ion (Li-ion) battery, whether in your phone or an EV, has four main components:

Cathode (Positive Electrode): This is what the question is about. It’s a lithium-based metal oxide. When you use the battery (discharge), the cathode releases lithium ions into the electrolyte. Common “chemistries” include NMC, NCA, and LFP.
Anode (Negative Electrode): This is where the graphite is. When you charge the battery, the anode stores the lithium ions within its structure.
Electrolyte: A liquid or gel that contains lithium salts. It acts as a shuttle, allowing only lithium ions to move between the cathode and anode.
Separator: A thin, porous membrane that keeps the cathode and anode physically separate. If they were to touch, it would cause a short circuit.

Why “Usually”? The Rise of LFP

The question uses the word “usually” because not all EV battery cathodes use nickel or cobalt. There is another major type:

LFP (Lithium Iron Phosphate, [latex]LiFePO_4[/latex]): This type of cathode uses iron and phosphate instead of nickel and cobalt.
- Pros: LFP batteries are cheaper, have a much longer lifespan (more charge cycles), and are considered safer as they are less prone to overheating.
- Cons: They have a lower energy density, which means the car has a shorter range for the same-sized battery pack.

Many automakers are now using LFP batteries for their standard-range models to reduce costs, while saving the more expensive, high-energy nickel-based (NMC/NCA) batteries for their long-range models.