Incremental Capacity Analysis

TLDR: dQ/dV doesn't interrogate your cell or demand a confession. It just looks closer at the answers your cell already gave you during a normal cycling test.

Differentiate the V vs. Q data you already collected, and the chemistry hiding inside a flat plateau jumps out as a sharp, traceable peak. No teardown, no new equipment, no drama. So fetch.

Incremental capacity analysis (ICA), better known by its equation name dQ/dV, is one of those techniques that feels like it should require something fancier than what it actually does. 

It gives you a fingerprint of the different electrochemical reactions happening in the cell, and a way to watch those reactions evolve, degrade, or vanish over hundreds of cycles.

Advantages:

What is dQ/dV Analysis?

During galvanostatic cycling, current is held constant and the voltage response is measured. Plotting capacity against voltage produces a profile that's either S-shaped or with flat plateaus, depending on the cell chemistry. The problem: small but meaningful changes in that curve are genuinely hard to see by eye. A plateau that's losing a little capacity each cycle just looks like... a slightly shorter plateau.

We can take the capacity (Q) and differentiate it with respect to voltage (V), then plot dQ/dV against V. Small plateaus become distinct peaks that are easier to visualize. Subtle shifts that were invisible in the raw curve are suddenly obvious and easy to track across cycles.