Electrolytes are solid, liquid or gel-like chemical substances that can absorb, release and transport ions to a sufficient degree.
The electrolyte is the medium for transferring ions between electrodes within the cell. Electrolytes serve the chemical reaction and take over the internal ion transport between the two electrodes, the anode and the cathode, in batteries, accumulators and fuel cells. To balance the charge, electrolytes generate ions, which, unlike electrons, can be transported in the electrolyte.
Looking at the circuit as a whole, a current of electrons flows from the connected circuit to the cathode, and from the cathode via the electrolyte to the anode. The current flow across the electrolyte is by means of cations and anions, the current flow with electrons from the anode across the circuit to the cathode.
In addition to liquid electrolytes, there are solid electrolytes used in solid oxide fuel cells, solid state batteries, and thin film batteries, as well as to generate ions at higher temperatures. In thin film batteries, the solid electrolyte used is lithium phosphorus oxynitride(LiPON). Sodium-sulfur batteries have a ceramic membrane made of aluminum oxide.