Deep eutectics and analogues as electrolytes in batteries

Deep Eutectic Solvents (DESs) are an emerging class of materials showing a marked depression in melting points compared to those of the neat constituents and characterized by a number of beneficial properties. DES research currently prospers and out of the multiple current applications, the electrochemistry field is likely the most flourishing. This detailed review emphasizes recent research efforts in order to apply type III and type IV DESs and their analogues as electrolytes for rechargeable cationic batteries. The recent developments in the last decade are outlined, framing outstanding achievements and open questions, and identifying future optimisation directions to overcome the existing challenges.