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

The practical applications of Li-O-2 batteries are hindered by the large charge polarization. Recently, the development of redox mediators (RMs) brings new hope for constructing low overpotential Li-O-2 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-O-2 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 I-3(-) ions to suppress the shuttle effect. As a result, the Li-O-2 battery shows a good cycling performance with eliminated self-discharge, and the Li anode is successfully protected by the inhibition of I-3(-) shuttling. This novel approach may provide new insights into the development of functionalized gel polymer electrolytes for Li-O-2 batteries with redox mediators.