TWO MECHANISMS

Inside the material, or on its surface

🧱

🔋

Battery

Ions go into the bulk of the electrodes through redox reactions

⚡

Supercapacitor

Ions pile up on a huge electrode surface in the double layer

🔀

Pseudocapacitor

Fast redox right at the surface, in between the two

Bulk storage holds more; surface storage is faster.

SPOT THE DEVICE

Supercapacitor or lithium-ion?

Each job favours one device or the other. Think about how much energy it needs, how fast, and how many times.

Energy for long runs, power for short bursts.

THE RAGONE PLOT

Energy versus power

A Ragone plot puts specific energy on one axis and specific power on the other. Batteries sit high and to the left; supercapacitors low and to the right.

No device sits in the top right corner, yet.

HEAD TO HEAD

How they compare

📋

Energy Lithium-ion about 150–300 Wh/kg; supercapacitors about 5–10 Wh/kg

Charge time Battery: tens of minutes to hours. Supercap: seconds

Cycle life Battery: hundreds to thousands. Supercap: hundreds of thousands to a million

Voltage curve Battery: fairly flat. Supercap: falls in a straight line as it empties

They are partners more often than rivals.

BEST OF BOTH

Hybrids

🤝

🔋⚡

Lithium-ion capacitor

A battery-type anode with a capacitor-type cathode

🚌

Hybrid packs

Supercaps take the regenerative braking spikes; batteries carry the range

🔗

More in the Supercapacitors course

See how the double layer works in detail

Pair a battery and a supercap and each covers the other's weak spot.

UNIT 5 STUDY COMPLETE

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Ready for the Fab Challenge?

You've compared storing charge in the bulk of a material with storing it on a surface, and seen where each one wins.