Sulfonated Bacterial Cellulose-Based Functional Gel Polymer Electrolyte for Li–O2 Batteries with LiI as a Redox Mediator

The practical applications of Li–O2 batteries are hindered by the large charge polarization. Recently, the development of redox mediators (RMs) brings new hope for constructing low overpotential Li–O2 batteries. However, the “shuttle effect” of RMs causes new problems. Here, based on a low-cost and environmentally friendly biomaterial–bacterial cellulose, a sulfonation strategy was adopted to produce a functional gel polymer electrolyte for LiI-involved Li–O2 batteries. Benefiting from the high-density negatively charged sulfonate groups on the sulfonated bacterial cellulose, the functionalized gel electrolyte can produce strong electrostatic repulsion force to the negatively charged I3– ions to suppress the shuttle effect. As a result, the Li–O2 battery shows a good cycling performance with eliminated self-discharge, and the Li anode is successfully protected by the inhibition of I3– shuttling. This novel approach may provide new insights into the development of functionalized gel polymer electrolytes for Li–O2 batteries with redox mediators.