Method
Smoothing dQ/dV: check the effect on peaks
Differential capacity underpins most incremental-capacity work, and it is also the plot ordinary cleaning ruins most easily. The mechanism is simple, and worth understanding once.
Mechanism
Why the derivative is the problem
Differentiating a noisy signal amplifies the noise, and the amplification grows as the spacing between samples shrinks. A voltage trace that looks perfectly usable turns into a dQ/dV curve where the noise reaches the height of the third peak.
The first instinct is to smooth the result until it looks like the figure in the paper you are comparing against. That is where the trap is.
Smoothing can shift or distort dQ/dV features. The effect depends on the method, its settings, the sampling grid and the feature shape. Compare the relevant features before accepting a processed curve.
A curve can look smoother while its features change. Record the processing settings and compare defined characteristics rather than accepting visual smoothness as validation.
What to do
Three rules and one check
Specify the preprocessing and derivative method
When smoothing is needed, compare processing before and after differentiation under the declared protocol. Record the method, parameters, grid and excluded intervals. Do not assume either choice preserves all features.
Keep measurement order and segment boundaries
Do not sort the original record to conceal reversals or combine distinct segments. A separately documented voltage-grid calculation may be appropriate within a selected monotonic segment; preserve the source-order mapping.
Compare before and after
Plot the original and the cleaned dQ/dV on the same grid and compare peak positions. If the apex has moved and you cannot say by how much, it is not yet clear whether your conclusion is about the cell or about the filter.
What a defensible workflow records: whether smoothing happened before or after the derivative; the method and its parameters; the evaluation grid — voltage bounds, step, interpolation, trimming; peak positions before and after with the shift; and which ranges were excluded from peak claims, and why.
Start
See your own raw dQ/dV
Confirm units and inspect valid intervals locally before smoothing. A numerical screening plot does not by itself establish cleaning need or electrochemical interpretation.