Suppressing Redox Shuttle with MXene-Modified Separators for Li-O2 Batteries.

Redox mediators (RMs) have been developed as efficient approaches to lower the charge polarization of Li-O2 batteries. However, the shuttle effect resulting from their soluble nature severely damages the battery performance, causing failure of the RM and anode corrosion. In this work, a chemical binding strategy based on a MXene-modified separator with a 3D porous hierarchical structure design was developed to suppress the I3- shutting in LiI-involved Li-O2 battery. As corroborated by experimental characterizations and theoretical calculations, the abundant -OH terminal groups on the MXene surface functioned as effective binding sites for suppressing the migration of I3-, while the 3D porous structure ensured the fast transfer of lithium ions. As a result, the Li-O2 battery with the MXene-modified separator showed no sign of redox shuttling compared with its counterparts in the full discharge/charge tests. In the meantime, the MXene-modified separator based-cell exhibited a stable cycle life up to 100 cycles, which is 3 times longer than the control samples. We believe that this work could provide insights into the development of separator modification for Li-O2 batteries with RMs.