Dual Active Site Covalent Organic Framework Anode Enables Stable Aqueous Proton Batteries.

Aqueous proton batteries (APBs) have attracted increasing interest owing to their potential for grid-scale energy storage with extraordinary sustainability and excellent rate abilities. However, there are limited anode materials and it remains a great challenge to effectively balance capacity and cycling performance. Here, we report a covalent organic framework containing C=O and C=N dual active sites (TABQ-COF) as a high-capacity and long-cycle anode for proton batteries. The proton storage ability of the dual active sites and the up to nine proton redox chemistry mechanisms for each repetitive unit have been demonstrated by experiments and density functional theory calculations. The insoluble TABQ-COF electrode displayed a remarkably high specific capacity of 401 mAh g, outstanding cycling stability (100 % capacity retention after 7500 cycles) and high rate performance (90 mAh g at 50 A g). When coupling with a MnO cathode, the constructed TABQ-COF//MnO battery achieves a reversible capacity of 247 mAh g at 5 A g, with a remarkable capacity retention of 100 % over 10000 cycles. Furthermore, the TABQ-COF//MnO battery can operate well and shows high capacity and cycle stability in a frozen electrolyte at -40°C, implying great potential for energy storage at extreme temperatures.