Protocol in evaluating capacity of Zn–Mn aqueous batteries: a clue of pH

• Main Authors: Yang, Hang, Zhang, Tengsheng, Chen, Duo, Tan, Yicheng, Zhou, Wanhai, Li, Li, Li, Wei, Li, Guangshe, Han, Wei, Fan, Hong Jin, Chao, Dongliang
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2023
• Subjects: Science::Chemistry; Aqueous Batteries; Battery Evaluation Protocol
• Online Access: https://hdl.handle.net/10356/170145
• Institution: Nanyang Technological University

In the literature, Zn–Mn aqueous batteries (ZMABs) confront abnormal capacity behavior, such as capacity fluctuation and diverse “unprecedented performances.” Because of the electrolyte additive-induced complexes, various charge/discharge behaviors associated with different mechanisms are being reported. However, the current performance assessment remains unregulated, and only the electrode or the electrolyte is considered. The lack of a comprehensive and impartial performance evaluation protocol for ZMABs hinders forward research and commercialization. Here, a pH clue (proton-coupled reaction) to understand different mechanisms is proposed and the capacity contribution is normalized. Then, a series of performance metrics, including rated capacity (Cr) and electrolyte contribution ratio from Mn2+ (CfM), are systematically discussed based on diverse energy storage mechanisms. The relationship between Mn (II) ↔ Mn (III) ↔ Mn (IV) conversion chemistry and protons consumption/production is well-established. Finally, the concrete design concepts of a tunable H+/Zn2+/Mn2+ storage system for customized application scenarios, opening the door for the next-generation high-safety and reliable energy storage system, are proposed.