Identifying the Role of Lewis‐base Sites for the Chemistry in Lithium‐Oxygen Batteries

Abstract

AbstractLewis‐base sites have been widely applied to regulate the properties of Lewis‐acid sites in electrocatalysts for achieving a drastic technological leap of lithium‐oxygen batteries (LOBs). Whereas, the direct role and underlying mechanism of Lewis‐base in the chemistry for LOBs are still rarely elucidated. Herein, we comprehensively shed light on the pivotal mechanism of Lewis‐base sites in promoting the electrocatalytic reaction processes of LOBs by constructing the metal–organic framework containing Lewis‐base sites (named as UIO‐66‐NH2). The density functional theory (DFT) calculations demonstrate the Lewis‐base sites can act as electron donors that boost the activation of O2/Li2O2 during the discharged‐charged process, resulting in the accelerated reaction kinetics of LOBs. More importantly, the in situ Fourier transform infrared spectra and DFT calculations firstly demonstrate the Lewis‐base sites can convert Li2O2 growth mechanism from surface‐adsorption growth to solvation‐mediated growth due to the capture of Li+ by Lewis‐base sites upon discharged process, which weakens the adsorption energy of UIO‐66‐NH2 towards LiO2. As a proof of concept, LOB based on UIO‐66‐NH2 can achieve a high discharge specific capacity (12 661 mAh g−1), low discharged‐charged overpotential (0.87 V) and long cycling life (169 cycles). This work reveals the direct role of Lewis‐base sites, which can guide the design of electrocatalysts featuring Lewis‐acid/base dual centers for LOBs.