The paper reports first on the electrochemical behavior in liquid Li
+
electrolytes of 200 nm thick single sol-gel (CeO
2
)
0.81
-TiO
2
electrochromic (EC) layers deposited by the dip-coating process. The electrolytes were solutions of 1 M LiCO
4
dissolved in dry propylene carbonate (PC) (containing 0.03wt% of water) and wet PC containing up to 10wt% of water, respectively. Then an electrochemical quartz crystal microbalance was used as a sensitive detector to analyze the mass changes occurring during the Li
+
ion exchange processes. These electrochemical processes were studied for 370 nm thick double layers, deposited on gold-coated quartz crystal electrodes and sintered at 450 °C in air. The electrolytes were the same solutions with water content varying from 0.03 up to 3wt% of water. The processes have been studied in the potential range from -2.0 to + 1.0 V vs. Ag/AgClO
4
during 100 voltammetry cycles. The composition of the (CeO
2
)
0.81
-TiO
2
layers was found to change during the early cycles, mainly because of an irreversible Li
+
intercalation. It was found, however, that the mass change observed during cycling is not due only to a pure Li
+
ion exchange process but also involves the adsorption/desorption or exchange of other cations and anions contained in the electrolyte. These ions are Li
+
and ClO
4
–
in dry electrolyte and Li
+
, hydrated Li(H
2
O)
n
+
and ClO
4
–
in wet electrolyte. The improvement of the reversibility of the intercalation and deintercalation processes as well as the faster kinetics observed in wet electrolytes are finally discussed in terms of a model in which the formation of hydrated Li
+
ions takes an important role.