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.