Interfacial thermodynamics-inspired electrolyte strategy to regulate output voltage and energy density of battery chemistry

Abstract

The electrochemical behaviors of battery chemistry, especially the operating voltage, are greatly affected by the complex electrode/electrolyte interface, but the corresponding basis understanding is still largely unclear. Herein, the concept of regulating electrode potential by interface thermodynamics is proposed, which guides the improvement of the energy density of Zn-MnO2 battery. A cationic electrolyte strategy is adopted to adjust the charge density of electrical double layer, as well as entropy change caused by desolvation, thus, achieving an output voltage of 1.6 V (vs. Zn2+/Zn) and a capacity of 400 mAh g−1. The detailed energy storage behaviors are also analyzed in terms of crystal field and energy level splitting. Furthermore, the electrolyte optimization benefits the efficient operation of Zn-MnO2 battery by enabling a high energy density of 532 Wh kg−1 based on the mass of cathode and a long cyclic life of more than 500 cycles. This work provides a path for designing high-energy-density aqueous battery via electrolyte strategy, which is expected to be extended to other battery systems.