The electrochemical window (EW) is an important concept in organic electrosynthesis and design of batteries, especially organic batteries. This is because at higher voltage (greater than 4.0 V) organic electrolytes decompose and interferes with the oxidation and reduction of the organic cathode/anode materials. For this reason, the best organic electrolytes should be characterized by a wider range of electrochemical window, i.e., greater than the working range of the  battery cell voltage. For example, the electrochemical window of Lithium bis- (trifluoromethanesulfonyl)imide, commercially known as LiTFSI is about 3.0 V because it can operate in the range of 1.9 -4.9 V. On the other hand, for electrolytes that are  characterized by narrow electrochemical window, they are prone to irreversible decomposition, which in turn triggers the battery capacity decaying during subsequent battery cycling.
The  electrochemical window of organic electrolyte  depends on many factors that include temperature, molecular frontier orbitals such LUMO (Lowest Unoccupied Molecular Orbital) and HOMO (Highest occupied Molecular Orbital) because the mechanisms of reduction (electron gaining) and oxidation (electron loss) are governed by band gap between HOMO and LUMO. Solvation energy also plays an important role in defining the electrochemical window of the electrolyte.
In order to safeguard the thermodynamic stability working conditions of the electrode materials in a given electrolyte, the electrochemical potentials of the electrode materials (anode and cathode) must be comprised within the electrochemical stability of the electrolyte. This condition is very succinct because electrolyte might be oxidized when the cathode material possess an electrochemical potential, which is less than the electrolyte oxidation potential. When the electrochemical potential of the anode material is quite higher than the reduction potential of the electrolyte, the electrolyte will be degraded through reduction process.