Theory-Driven Design of a Cationic Accelerator for High-Performance Electrolytic MnO₂ -Zn Batteries.

Abstract

Aqueous electrolytic MnO₂ -Zn batteries are considered as one of the most promising energy-storage devices for their cost effectiveness, high output voltage, and safety, but their electrochemical performance is limited by the sluggish kinetics of cathodic MnO₂ /Mn²⁺ and anodic Zn/Zn²⁺ reactions. To overcome this critical challenge, herein, a cationic accelerator (CA) strategy is proposed based on the prediction of first-principles calculations. Poly(vinylpyrrolidone) is utilized as a model to testify the rational design of the CA strategy. It manifests that the CA effectively facilitates rapid cations migration in electrolyte and adequate charge transfer at electrode-electrolyte interface, benefiting the deposition/dissolution processes of both Mn²⁺ and Zn²⁺ cations to simultaneously improve kinetics of cathodic MnO₂ /Mn²⁺ and anodic Zn/Zn²⁺ reactions. The resulting MnO₂ -Zn battery regulated by CA exhibits large reversible capacities of 455 mAh g^-1 and 3.64 mAh cm^-2 at 20 C, as well as a long lifespan of 2000 cycles with energy density retention of 90%, achieving one of the best overall performances in the electrolytic MnO₂ -Zn batteries. This comprehensive work integrating theoretical prediction with experimental studies provides opportunities to the development of high-performance energy-storage devices.