Protocol in Evaluating Capacity of Zn–Mn Aqueous Batteries: A Clue of pH

Abstract

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.

Fast Ionic Conducting Hydroxyapatite Solid Electrolyte Interphase Enables Ultra-Stable Zinc Metal Anodes

“…The slight fading observed in the 400 to 500 cycles can be attributed to either structural distortion or Mn dissolution in MnO 2 during the prolonged cycling period (Figure 6c). 29,54 In contrast, despite that bare Zn||MnO 2 presents a similar initial capacity of 230.4 mAh g −1 , the capacity swiftly decreases to less than 100 mAh g −1 within only 50 cycles (Figure 6d). Furthermore, the rate performance of the full cells has been measured at different current densities varying from 0.2 to 5 A g −1 , as depicted in Figure 6e.…”

Atomic scale analysis of Zn2+ storage in robust tunnel frameworks

“…MnO 2 experiences significant dissolution, while VO 2 and V 2 O 3 undergo phase transformations to layered V 2 O 5 · n H 2 O during charging. 11 b ,11 c ,11 e ,23 In comparison, MVT-M1 emerges as the most suitable material for investigating the atomic-scale insertion and extraction of Zn 2+ during discharge and charge processes using HAADF-STEM. This aspect is crucial for comprehending the Zn 2+ storage mechanism and designing novel materials tailored for efficient Zn 2+ storage.…”

A eutectic electrolyte for an ultralong-lived Zn//V2O5cell: anin situgenerated gradient solid-electrolyte interphase

“…Zn is particularly promising due to its moderate chemical activity, which allows for cost-effective processing and compatibility with aqueous media. 11–15 Additionally, its abundance is hundreds of times higher than that of lithium, making it suitable for low-cost, large-scale applications. Zn ion batteries also have a high theoretical specific capacity (820 mA h g −1 ) and offer eco-friendly ease of use and safety, making them a promising future energy storage technology.…”