posted on 2023-07-10, 14:37authored byZhengnan Tian, Vinayak S. Kale, Zixiong Shi, Jian Yin, Sharath Kandambeth, Yizhou Wang, Abdul-Hamid Emwas, Yongjiu Lei, Xianrong Guo, Jun Ming, Wenxi Wang, Norah Alsadun, Osama Shekhah, Mohamed Eddaoudi, Husam N. Alshareef
Proton activity in electrolytes plays a crucial role
in deciding
the electrochemical performance of aqueous batteries. On the one hand,
it can influence the capacity and rate performance of host materials
because of the high redox activity of protons. On the other hand,
it can also cause a severe hydrogen evolution reaction (HER) when
the protons are aggregated near the electrode/electrolyte interface.
The HER dramatically limits the potential window and the cycling stability
of the electrodes. Therefore, it is critical to clarify the impact
of electrolyte proton activity on the battery macro-electrochemical
performance. In this work, using an aza-based covalent organic framework
(COF) as a representative host material, we studied the effect of
electrolyte proton activity on the potential window, storage capacity,
rate performance, and cycle stability in various electrolytes. A tradeoff
relationship between proton redox reactions and the HER in the COF
host is revealed by utilizing various in situ and ex situ characterizations.
Moreover, the origin of proton activity in near-neutral electrolytes
is discussed in detail and is confirmed to be related to the hydrated
water molecules in the first solvation shell. A detailed analysis
of the charge storage process in the COFs is presented. These understandings
can be of importance for utilizing the electrolyte proton activity
to build high-energy aqueous batteries.