Rational reconfiguration of a gradient redox mediator with in-situ fabricated gel electrolyte for Li–air batteries

Flexible lithium–air batteries (LABs) with a redox mediator (RM) in the electrolyte demonstrate enhanced round-trip efficiency. However, their cycle performance is unsatisfactory due to severe corrosion of the Li metal anode. Herein, we propose a two step gelatinization strategy to fabricate a gradient RMs (including LiI, TMPD, and DMPZ) gel electrolyte, in which the bare electrolyte gelatinization on the Li surface and then the electrolyte contained RMs sequentially gelled on the formed gel. The RMs mainly distributed at the surface and anchored at the cathode side. By suppressing the shuttle of RMs in the electrolyte and alleviating the passivation of the Li anode, the mid-charging potentials can reach 3.44 and 4.08 V at the 15th cycle with and without the LiI mediator, respectively. The energy efficiency is 63% even at the 150th cycle, whereas the corresponding energy efficiency are only 47% and 51% for the LABs with liquid and normal gel electrolytes, respectively. Moreover, the cycle life of the battery containing the gradient gel electrolyte is three times longer than that with the liquid electrolyte. The gel electrolyte further offers the flexibility of the device, and the laminated cells thus fabricated can readily operate under harsh bending conditions.