Universality of Benzoquinone-based Anodes toward Various Metal Cations in Aqueous Rechargeable Batteries

The poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (denoted as PDBM) capable of reversible coordination/uncoordination with both mono- and multivalent cations in aqueous electrolytes is desired to develop safe, sustainable, and cost-effective aqueous rechargeable batteries (ARBs). However, the comprehensive mechanism between the electrochemical performance of PDBM and properties of these metal cations is unclear. Herein, we initially demonstrate the universality of PDBM to reversibly coordinate/uncoordinate with various cations (Na+, Mg2+, Ca2+, Zn2+, Al3+, etc.) with high specific capacities (>200 mA h g(-1)), high rate capabilities (similar to 20 C), and long cycling life (5000 cycles). Additionally, an unprecedented ion-coordination mechanism is presented: the monovalent cations prefer to occupy the in-plane sites with respect to the benzene rings of PDBM during the electrochemical reduced process, while the multivalent cations with the larger charge density tend to occupy the out-of-plane sites, which can use more active sites in the PDBM molecule and deliver the higher specific capacities. Meanwhile, the redox potential of PDBM decreases with the decrease in the binding energy between metal cations and PDBM molecules. The universality of PDBM to numerous cations is beneficial to design high-safety, low-cost, and long-lifespan ARBs for large-scale energy storage systems by modulating the aqueous electrolytes.

Automated summary

This study demonstrates the universality of poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM) to reversibly coordinate/uncoordinate with various cations, leading to high specific capacities, high rate capabilities, and long cycling life in aqueous electrolytes. The research reveals an unprecedented ion-coordination mechanism and highlights the correlation between metal cations and the electrochemical performance of PDBM. The universality of PDBM to numerous cations can be beneficial for designing safe, cost-effective, and long-lifespan aqueous rechargeable batteries (ARBs) for large-scale energy storage systems.