I have studied cathode materials for LIBs

I synthesized the two materials and conducted EIS test.

The only difference between the two materials is that B is doped at F 1 at%.

but the Nyquist flot shows a different shape.

A shows two semicircles and B shows one semicircle.

(1) why there is such a difference.

(2) how to interpret the graph.(A an B)

When I studied at the other references, there was only one semicircle on the graph.

Is the first semicircle Rs and the second semicircle Rct?

If so, how should we interpret case B?

10mHz to 100K Hz

Amplitude : 5mV