Light‐Assisted Li–O₂ Batteries with Lowered Bias Voltages by Redox Mediators

Abstract

The enormous overpotential caused by sluggish kinetics of the oxygen reduction reaction and the oxygen evolution reaction prevents the practical application of Li–O2 batteries. The recently proposed light‐assisted strategy is an effective way to improve round‐trip efficiency; however, the high‐potential photogenerated holes during the charge would degrade the electrolyte with side reactions and poor cycling performance. Herein, a synergistic interaction between a polyterthiophene photocatalyst and a redox mediator is employed in Li–O2 batteries. During the discharge, the voltage can be compensated by the photovoltage generated on the photoelectrode. Upon the charge with illumination, the photogenerated holes can be consumed by the oxidization of iodide ions, and thus the external circuit voltage is compensated by photogenerated electrons. Accordingly, a smaller bias voltage is needed for the semiconductor to decompose Li2O2, and the potential of photogenerated holes decreases. Finally, the round‐trip efficiency of the battery reaches 97% with a discharge voltage of 3.10 V and a charge voltage of 3.19 V. The batteries show stable operation up to 150 cycles without increased polarization. This work provides new routes for light‐assisted Li–O2 batteries with reduced overpotential and boosted efficiency.

Field‐assisted electrocatalysts spark sulfur redox kinetics: From fundamentals to applications

“…[128,137] Exception of the enhanced charge transfer kinetics, the smaller voltage polarization is conquered, which is ascribed to the compensation of photoelectrons/holes in the cathode reactions. [138] Furthermore, as inspired by research on Li-O 2 batteries, [139][140][141] the origin of intensified electrocatalytic reactivity might also be expanded to regulate Li 2 S growth/deposition or mediate thermodynamic pathways. Regrettably, the small window for accepting light is always arranged near the back of the cathode, [26] and the resultant limited visible light utilization and inhomogeneous light intensity across the cathode make it remain at the conception stage.…”

Light‐Assisted Metal–Air Batteries: Progress, Challenges, and Perspectives

“…[116] Recently, pTTh coupled with I 3 À /I À as redox mediators was used to reduce the overpotentials of a Li-O 2 battery. [76] Photoelectrons contributed to the ORR process, while holes oxidized I À to I 3 À and decomposed Li 2 O 2 , resulting in a lowered charge voltage of 3.19 V.…”

“…Recently, lightassisted batteries with redox mediators have been reported to have superior stability because more holes would be consumed by the oxidation reactions of iodide ions instead of attacking the electrolyte. [76] Solid-state electrolytes are considered more suitable choices than liquid electrolytes for open light-assisted battery systems due to their better photo/thermal/chemical stability. Li 2 OÀ Al 2 O 3 À GeO 2 À P 2 O 5 (LAGP) electrolytes have been used in photothermal promoted Li-air batteries, which could bear the extremely high temperature up to 120 °C.…”

Stepping Up the Kinetics of Li–O2 Batteries by Shrinking Down the Li2O2 Granules through Concertedly Enhanced Catalytic Activity and Photoactivity of Se-Doped LaCoO3

“…The ever-escalating environmental and energy crises around the globe have put forward the research and development of advanced energy storage devices as a high priority. − Rechargeable Li–O 2 batteries (LOBs), owing to the high theoretical energy density of 3505 Wh kg –1 and exploitation of inexhaustible oxygen as the cathode active material, have attracted particular interests among battery researchers. − However, the deployment of the LOB technology is still in its infancy, with some critical challenges still to be dealt with, including the low round-trip energy efficiency caused by large charge/discharge polarization, the hazardous side reactions caused by high charging potential, and the accumulative deposition of insulative Li 2 O 2 and Li 2 CO 3 products that impede both charge and mass transfer. − In order to address these issues, several strategic solutions have been proposed and implemented at both the material and device levels. These include the fabrication of highly efficient oxygen cathode catalysts (e.g., carbon materials, noble metals, metal organic frameworks, and heterostructured electrocatalysts) to kinetically expedite both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the supplement of redox mediators (e.g., I – /I 3 – , , TEMPO , ) into the electrolyte to lower both the thermodynamic and kinetic barriers of internal charge transfer, as well as the application of external fields (e.g., photovoltaic, − electromagnetic) to complement the electric energy with other energy formats. In this context, the development of highly efficient field-sensitive catalysts with both enhanced ORR and OER activities is pivotal to advance the field-assisted LOB technology.…”