Li-O 2 batteries with ultrahigh theoretical energy densities usually suffer from low practical discharge capacities and inferior cycling stability owing to the cathode passivation caused by insulating discharge products and by-products. Here, we firstly introduce a new kind of trifunctional ether-based redox mediator, 2,5-di-tert-butyl-1,4-dimethoxybenzene (DBDMB), into the electrolyte to capture the reactive O 2 - and alleviate the rigorous oxidative environment during cycling of Li-O 2 batteries. Thanks to the strong solvation of DBDMB towards Li + and O 2 - , it can not only reduce the formation of by-products (a high Li 2 O 2 yield of 96.6%), but also promote the solution growth of large-sized Li 2 O 2 particles, avoiding the passivation of cathode as well as enabling a large discharge capacity. More encouragingly, DBDMB makes the oxidization of Li 2 O 2 and the decomposition of main by-products (Li 2 CO 3 and LiOH) proceed in a highly effective manner, prolonging the stability of Li-O 2 batteries (243 cycles at 1000 mAh g -1 and 1000 mA g -1 ). DFT calculations also unravel the intrinsic functional mechanism of DBDMB for facilitating the reversible O 2 involved redox reactions. Our strategy of using trifunctional electrolyte additive to capture reactive discharge intermediates with reduced formation of by-products, regulate solution growth of Li 2 O 2 , and co-oxidize Li 2 O 2 and by-products, will open up a new avenue to promote the performance of Li-air batteries.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was financially supported by the National Key R&D Program of China (2017YFA0206700), the National Natural Science Foundation of China (21725103, 51702314), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA21010210), the Jilin Province Science and Technology Development Plan Funding Project (20180101203JC), the K. C. Wong Education Foundation (GJTD2018-09), the Changchun Science and Technology Development Plan Funding Project (19SS010) and the National & local united
engineering lab for power battery. The Supercomputing USTC is acknowledged for computational support.