Molecular crowding agents engineered to make bioinspired electrolytes for high-voltage aqueous supercapacitors

The development of low-cost and eco-friendly aqueous electrolytes with a wide voltage window is the key to achieving safe high energy density supercapacitors (SCs). In this work, a molecular crowding electrolyte is prepared by simulating the crowded environment in living cells. Ion transport in the molecular crowding electrolyte can be effectively improved via reducing the molecular weight of the crowding agent, polyethylene glycol (PEG). The results show that PEG with a molecular weight of 200 (PEG200) can significantly improve ionic conductivity while maintaining a wide voltage window. These advantages enable commercial activated carbon-based SCs to work at 2.5 V with high energy density, outstanding rate performance and good stability for more than 10,000 cycles. On this basis, three series of molecular crowding electrolytes using sodium perchlorate, lithium perchlorate, and sodium trifluoromethanesulfonate as salts are developed, demonstrating the versatility of PEG200 for wide-voltage aqueous electrolytes.