A long-life lithium-oxygen battery via a molecular quenching/mediating mechanism

Abstract

Lithium-oxygen (Li-O2) batteries have drawn intensive attention owing to their exceptionally high theoretical specific energy. However, their further advancement has been significantly hindered by challenges including low discharge capacity, poor energy efficiency, severe parasitic reactions, etc. Here, we report a highly Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2 nanoparticles. The battery exhibits a 46-fold increase of discharge capacity, a low charge over-potential of 0.7 V, and an ultralong cycle life > 1400 cycles. The tailor-designed organic molecule features two redox mediator-active 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) moieties bridged by a quenching-active perylene diimide (PDI) backbone. The PDI-TEMPO molecule not only acts as a soluble redox mediator to catalyze both discharge and charge reactions, but also serves as a reusable superoxide radical quencher to chemically react with superoxide species generated during the operation of Li-O2 batteries, leading to the formation of Li2O2 nanoparticles which are much easier to decompose than the conventional toroidal-shaped Li2O2. The all-in-one molecule as a multifunctional additive can tackle various issues of parasitic reactions associated with superoxide radicals, singlet oxygen, high over-potentials, and lithium corrosion, beyond the mere combination of PDI and TEMPO moieties’ functionalities. The molecular design of multifunctional additives combining the capabilities of redox mediators, superoxide radical quencher and beyond opens a new avenue for developing high-performance Li-O2 batteries.

Enhancing the Reaction Kinetics and Reversibility of Li–O2 Batteries by Multifunctional Polymer Additive

“…[36,39,41] Hence, PTFEMA-present Li-O 2 cell with low R ct value also implies good reversibility of Li 2 O 2 and by-product accumulation suppression during cycling. 1 H NMR spectra measurement of D 2 O-extracted cathodic plate and separator from corresponding cycled Li-O 2 cell (20 cycles) is further carried out to investigate possible byproducts during cycling. The peak area of internal standard benzene is normalized before rational comparison.…”

“…Characterized with the ultrahigh theoretical energy density of 3500 wh kg −1 , Li-O 2 batteries (LOBs) have been recognized as a promising next-generation energy storage system. [1][2][3][4] However, introduction of O 2 atmosphere nevertheless exacerbates the complexity of LOBs. As a unique open battery system, LOBs are confronted with critical tough issues: sluggish oxygen electrochemical performance of LOBs with poor cycle life, which hinders its further commercial application.…”

“…[11,[16][17][18] However, the utilization of sole electrolyte additives is a simple and proveneffective strategy for improving the electrochemical performance of LOBs. [1,19] Polymers, with reliable flexibility, suitable mechanical strength, and good electrochemical stability, are used widely as solid or quasi-solid electrolytes in the batteries field. [20][21][22][23] However, low ionic conductivity and stiff interface contact are inevitable and tough issues of polymer electrolytes in batteries.…”

“…Characterized with the ultrahigh theoretical energy density of 3500 wh kg −1 , Li–O 2 batteries (LOBs) have been recognized as a promising next‐generation energy storage system. [ 1–4 ] However, introduction of O 2 atmosphere nevertheless exacerbates the complexity of LOBs. As a unique open battery system, LOBs are confronted with critical tough issues: sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics, poor irreversibility and rechargeability, detrimental superoxide‐derived parasitic reactions, and Li‐metal anode corrosion, which all need to be solved urgently before further application.…”

Lithium Salt Dissociation Promoted by 18‐Crown‐6 Ether Additive toward Dilute Electrolytes for High Performance Lithium Oxygen Batteries

“…Lithium-oxygen batteries (LOBs) demonstrate the promising prospects of long-range electric vehicles and portable power equipment owning to their high theoretical energy density ( � 3500 Wh kg À 1 ). [1] However, multi-step ORR/OER reactions lead to sluggish kinetics of LOBs. The insulating discharge product Li 2 O 2 is easy to block the pores in cathodes and cause battery "sudden death".…”