Manipulating electrolyte solvation structures to build high-voltage concentration batteries for efficient energy storage

Concentration batteries represent a distinctive type of Galvanic cells that use the same redox couple at both electrodes but generate voltage from differences in electrolyte compositions. However, their applications have been limited because ten times concentration difference typically produces only small voltages (<0.059 volts, V). Here we show that tailoring electrolyte properties can overcome this limitation and enable metal-based (zinc and copper) concentration batteries with higher voltages. By using a highly concentrated catholyte electrolyte, the redox potential of the positive electrode is increased, while a strongly complexing anolyte electrolyte lowers the free ion concentration and decreases the redox potential of the negative electrode. This asymmetric electrolyte design produces a cell voltage of 0.6-0.7 V, which is higher than the preconceived notion of 0.059 V. Furthermore, this approach can be combined with common positive electrodes to fabricate aqueous full cells with higher voltages (2.2-2.5 V), therefore boosting their voltages and specific energy densities.