In the process of finding new forms of energy extraction or recovery, the use of various natural systems as potential clean and renewable energy sources has been examined. Blue energy is an interesting energy alternative based on chemical energy that is spontaneously released when mixing water solutions with different salt concentrations. This occurs naturally in the discharge of rivers into ocean basins on such a scale that it justifies efforts for detailed research. This article collects the most relevant information from the latest publications on the topic, focusing on the use of the mixing entropy battery (MEB) as an electrochemical ion pumping device and the different technological means that have been developed for the conditions of this process. In addition, it describes various practices and advances achieved by various researchers in the optimization of this device, in relation to the most important redox reactions and the cathode and anodic materials used for the recovery of blue energy or salinity gradient energy.