Although electrochemical transistors have been widely explored for memory devices, there is still a lack of in-depth understanding of their mechanism in the devices with ionogels. In this study, we present a set of complementary analytical approaches to capture the working mechanisms of the devices and elucidate the fundamental principles of their memory behaviors. Electrochemical impedance spectroscopy revealed that, as the composition of the ionic species decreased, the ionic motion under the gate electric field became dominant. We also found that the dense polymer matrix of the electrolyte can restrict the motion of bulky ions under a constant gate current, effectively reducing the ion conductivity. Repeated tests of transient responses revealed that the devices with an electronic channel layer with a relatively low permeability of ions showed suppressed diffusion-induced charge transport at the electrolyte-channel interface, eventually reaching the non-volatile characteristics.