Based on a distortive lattice gas model we have investigated the intercalation of ions into a host material. It is shown that an effective potential for the ions results from the intercalation-induced distortion of the host. This interaction induces a distinct peak in the current-concentration diagram. The peak reveals a droplet formation around the distorted host domains. Theoretical results agree with experimental values for LixTiS2. The ionic permselectivity effect is found to play a prominent role for the electrochemical intercalation.